rgb24toyuv use 1 or 2 steps consistently.

R=bcornell@google.com, impjdi@google.com
BUG=libyuv:459

Review URL: https://webrtc-codereview.appspot.com/52149004.

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1440
+Version: 1441
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 1440
+#define LIBYUV_VERSION 1441
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/convert.cc

@@ -817,22 +817,20 @@ int RGB24ToI420(const uint8* src_rgb24, int src_stride_rgb24,
     src_stride_rgb24 = -src_stride_rgb24;
   }
 
+// Neon version does direct RGB24 to YUV.
 #if defined(HAS_RGB24TOYROW_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
+    RGB24ToUVRow = RGB24ToUVRow_Any_NEON;
     RGB24ToYRow = RGB24ToYRow_Any_NEON;
     if (IS_ALIGNED(width, 8)) {
       RGB24ToYRow = RGB24ToYRow_NEON;
+      if (IS_ALIGNED(width, 16)) {
+        RGB24ToUVRow = RGB24ToUVRow_NEON;
+      }
     }
   }
-#endif
-#if defined(HAS_RGB24TOUVROW_NEON)
-  if (TestCpuFlag(kCpuHasNEON)) {
-    RGB24ToUVRow = RGB24ToUVRow_Any_NEON;
-    if (IS_ALIGNED(width, 16)) {
-      RGB24ToUVRow = RGB24ToUVRow_NEON;
-    }
-  }
-#endif
+// Other platforms do intermediate conversion from RGB24 to ARGB.
+#else
 #if defined(HAS_RGB24TOARGBROW_SSSE3)
   if (TestCpuFlag(kCpuHasSSSE3)) {
     RGB24ToARGBRow = RGB24ToARGBRow_Any_SSSE3;
@@ -861,7 +859,6 @@ int RGB24ToI420(const uint8* src_rgb24, int src_stride_rgb24,
     }
   }
 #endif
-#if !defined(HAS_RGB24TOYROW_NEON)
   {
     // Allocate 2 rows of ARGB.
     const int kRowSize = (width * 4 + 31) & ~31;
@@ -934,22 +931,20 @@ int RAWToI420(const uint8* src_raw, int src_stride_raw,
     src_stride_raw = -src_stride_raw;
   }
 
+// Neon version does direct RAW to YUV.
 #if defined(HAS_RAWTOYROW_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
+    RAWToUVRow = RAWToUVRow_Any_NEON;
     RAWToYRow = RAWToYRow_Any_NEON;
     if (IS_ALIGNED(width, 8)) {
       RAWToYRow = RAWToYRow_NEON;
+      if (IS_ALIGNED(width, 16)) {
+        RAWToUVRow = RAWToUVRow_NEON;
+      }
     }
   }
-#endif
-#if defined(HAS_RAWTOUVROW_NEON)
-  if (TestCpuFlag(kCpuHasNEON)) {
-    RAWToUVRow = RAWToUVRow_Any_NEON;
-    if (IS_ALIGNED(width, 16)) {
-      RAWToUVRow = RAWToUVRow_NEON;
-    }
-  }
-#endif
+// Other platforms do intermediate conversion from RAW to ARGB.
+#else
 #if defined(HAS_RAWTOARGBROW_SSSE3)
   if (TestCpuFlag(kCpuHasSSSE3)) {
     RAWToARGBRow = RAWToARGBRow_Any_SSSE3;
@@ -978,7 +973,6 @@ int RAWToI420(const uint8* src_raw, int src_stride_raw,
     }
   }
 #endif
-#if !defined(HAS_RAWTOYROW_NEON)
   {
     // Allocate 2 rows of ARGB.
     const int kRowSize = (width * 4 + 31) & ~31;
@@ -1051,18 +1045,20 @@ int RGB565ToI420(const uint8* src_rgb565, int src_stride_rgb565,
     src_stride_rgb565 = -src_stride_rgb565;
   }
 
+// Neon version does direct RGB565 to YUV.
 #if defined(HAS_RGB565TOYROW_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
+    RGB565ToUVRow = RGB565ToUVRow_Any_NEON;
     RGB565ToYRow = RGB565ToYRow_Any_NEON;
     if (IS_ALIGNED(width, 8)) {
       RGB565ToYRow = RGB565ToYRow_NEON;
-    }
-    RGB565ToUVRow = RGB565ToUVRow_Any_NEON;
-    if (IS_ALIGNED(width, 16)) {
-      RGB565ToUVRow = RGB565ToUVRow_NEON;
+      if (IS_ALIGNED(width, 16)) {
+        RGB565ToUVRow = RGB565ToUVRow_NEON;
+      }
     }
   }
-#endif
+// Other platforms do intermediate conversion from RGB565 to ARGB.
+#else
 #if defined(HAS_RGB565TOARGBROW_SSE2)
   if (TestCpuFlag(kCpuHasSSE2)) {
     RGB565ToARGBRow = RGB565ToARGBRow_Any_SSE2;
@@ -1099,7 +1095,6 @@ int RGB565ToI420(const uint8* src_rgb565, int src_stride_rgb565,
     }
   }
 #endif
-#if !defined(HAS_RGB565TOYROW_NEON)
   {
     // Allocate 2 rows of ARGB.
     const int kRowSize = (width * 4 + 31) & ~31;
@@ -1172,19 +1167,20 @@ int ARGB1555ToI420(const uint8* src_argb1555, int src_stride_argb1555,
     src_stride_argb1555 = -src_stride_argb1555;
   }
 
+// Neon version does direct ARGB1555 to YUV.
 #if defined(HAS_ARGB1555TOYROW_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
+    ARGB1555ToUVRow = ARGB1555ToUVRow_Any_NEON;
     ARGB1555ToYRow = ARGB1555ToYRow_Any_NEON;
     if (IS_ALIGNED(width, 8)) {
       ARGB1555ToYRow = ARGB1555ToYRow_NEON;
-    }
-    ARGB1555ToUVRow = ARGB1555ToUVRow_Any_NEON;
-    if (IS_ALIGNED(width, 16)) {
-      ARGB1555ToUVRow = ARGB1555ToUVRow_NEON;
+      if (IS_ALIGNED(width, 16)) {
+        ARGB1555ToUVRow = ARGB1555ToUVRow_NEON;
+      }
     }
   }
-#endif
-
+// Other platforms do intermediate conversion from ARGB1555 to ARGB.
+#else
 #if defined(HAS_ARGB1555TOARGBROW_SSE2)
   if (TestCpuFlag(kCpuHasSSE2)) {
     ARGB1555ToARGBRow = ARGB1555ToARGBRow_Any_SSE2;
@@ -1221,12 +1217,12 @@ int ARGB1555ToI420(const uint8* src_argb1555, int src_stride_argb1555,
     }
   }
 #endif
-#if !defined(HAS_ARGB1555TOYROW_NEON)
   {
     // Allocate 2 rows of ARGB.
     const int kRowSize = (width * 4 + 31) & ~31;
     align_buffer_64(row, kRowSize * 2);
 #endif
+
     for (y = 0; y < height - 1; y += 2) {
 #if defined(HAS_ARGB1555TOYROW_NEON)
       ARGB1555ToUVRow(src_argb1555, src_stride_argb1555, dst_u, dst_v, width);
@@ -1236,6 +1232,7 @@ int ARGB1555ToI420(const uint8* src_argb1555, int src_stride_argb1555,
 #else
       ARGB1555ToARGBRow(src_argb1555, row, width);
       ARGB1555ToARGBRow(src_argb1555 + src_stride_argb1555, row + kRowSize,
+
                         width);
       ARGBToUVRow(row, kRowSize, dst_u, dst_v, width);
       ARGBToYRow(row, dst_y, width);
@@ -1295,19 +1292,20 @@ int ARGB4444ToI420(const uint8* src_argb4444, int src_stride_argb4444,
     src_stride_argb4444 = -src_stride_argb4444;
   }
 
+// Neon version does direct ARGB4444 to YUV.
 #if defined(HAS_ARGB4444TOYROW_NEON)
   if (TestCpuFlag(kCpuHasNEON)) {
+    ARGB4444ToUVRow = ARGB4444ToUVRow_Any_NEON;
     ARGB4444ToYRow = ARGB4444ToYRow_Any_NEON;
     if (IS_ALIGNED(width, 8)) {
       ARGB4444ToYRow = ARGB4444ToYRow_NEON;
-    }
-    ARGB4444ToUVRow = ARGB4444ToUVRow_Any_NEON;
-    if (IS_ALIGNED(width, 16)) {
-      ARGB4444ToUVRow = ARGB4444ToUVRow_NEON;
+      if (IS_ALIGNED(width, 16)) {
+        ARGB4444ToUVRow = ARGB4444ToUVRow_NEON;
+      }
     }
   }
-#endif
-
+// Other platforms do intermediate conversion from ARGB4444 to ARGB.
+#else
 #if defined(HAS_ARGB4444TOARGBROW_SSE2)
   if (TestCpuFlag(kCpuHasSSE2)) {
     ARGB4444ToARGBRow = ARGB4444ToARGBRow_Any_SSE2;
@@ -1344,8 +1342,6 @@ int ARGB4444ToI420(const uint8* src_argb4444, int src_stride_argb4444,
     }
   }
 #endif
-
-#if !defined(HAS_ARGB4444TOYROW_NEON)
   {
     // Allocate 2 rows of ARGB.
     const int kRowSize = (width * 4 + 31) & ~31;

tools/protoc_wrapper/protoc_wrapper.py

+#!/usr/bin/env python
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+A simple wrapper for protoc.
+
+- Adds includes in generated headers.
+- Handles building with system protobuf as an option.
+"""
+
+import fnmatch
+import optparse
+import os.path
+import shutil
+import subprocess
+import sys
+import tempfile
+
+PROTOC_INCLUDE_POINT = '// @@protoc_insertion_point(includes)\n'
+
+def ModifyHeader(header_file, extra_header):
+  """Adds |extra_header| to |header_file|. Returns 0 on success.
+
+  |extra_header| is the name of the header file to include.
+  |header_file| is a generated protobuf cpp header.
+  """
+  include_point_found = False
+  header_contents = []
+  with open(header_file) as f:
+    for line in f:
+      header_contents.append(line)
+      if line == PROTOC_INCLUDE_POINT:
+        extra_header_msg = '#include "%s"\n' % extra_header
+        header_contents.append(extra_header_msg)
+        include_point_found = True;
+  if not include_point_found:
+    return 1
+
+  with open(header_file, 'wb') as f:
+    f.write(''.join(header_contents))
+  return 0
+
+def ScanForBadFiles(scan_root):
+  """Scan for bad file names, see http://crbug.com/386125 for details.
+  Returns True if any filenames are bad. Outputs errors to stderr.
+
+  |scan_root| is the path to the directory to be recursively scanned.
+  """
+  badname = False
+  real_scan_root = os.path.realpath(scan_root)
+  for dirpath, dirnames, filenames in os.walk(real_scan_root):
+    matches = fnmatch.filter(filenames, '*-*.proto')
+    if len(matches) > 0:
+      if not badname:
+        badname = True
+        sys.stderr.write('proto files must not have hyphens in their names ('
+                         'see http://crbug.com/386125 for more information):\n')
+      for filename in matches:
+        sys.stderr.write('  ' + os.path.join(real_scan_root,
+                                             dirpath, filename) + '\n')
+  return badname
+
+
+def RewriteProtoFilesForSystemProtobuf(path):
+  wrapper_dir = tempfile.mkdtemp()
+  try:
+    for filename in os.listdir(path):
+      if not filename.endswith('.proto'):
+        continue
+      with open(os.path.join(path, filename), 'r') as src_file:
+        with open(os.path.join(wrapper_dir, filename), 'w') as dst_file:
+          for line in src_file:
+            # Remove lines that break build with system protobuf.
+            # We cannot optimize for lite runtime, because system lite runtime
+            # does not have a Chromium-specific hack to retain unknown fields.
+            # Similarly, it does not understand corresponding option to control
+            # the usage of that hack.
+            if 'LITE_RUNTIME' in line or 'retain_unknown_fields' in line:
+              continue
+            dst_file.write(line)
+
+    return wrapper_dir
+  except:
+    shutil.rmtree(wrapper_dir)
+    raise
+
+
+def main(argv):
+  parser = optparse.OptionParser()
+  parser.add_option('--include', dest='extra_header',
+                    help='The extra header to include. This must be specified '
+                         'along with --protobuf.')
+  parser.add_option('--protobuf', dest='generated_header',
+                    help='The c++ protobuf header to add the extra header to. '
+                         'This must be specified along with --include.')
+  parser.add_option('--proto-in-dir',
+                    help='The directory containing .proto files.')
+  parser.add_option('--proto-in-file', help='Input file to compile.')
+  parser.add_option('--use-system-protobuf', type=int, default=0,
+                    help='Option to use system-installed protobuf '
+                         'instead of bundled one.')
+  (options, args) = parser.parse_args(sys.argv)
+  if len(args) < 2:
+    return 1
+
+  if ScanForBadFiles(options.proto_in_dir):
+    return 1
+
+  proto_path = options.proto_in_dir
+  if options.use_system_protobuf == 1:
+    proto_path = RewriteProtoFilesForSystemProtobuf(proto_path)
+  try:
+    # Run what is hopefully protoc.
+    protoc_args = args[1:]
+    protoc_args += ['--proto_path=%s' % proto_path,
+                    os.path.join(proto_path, options.proto_in_file)]
+    ret = subprocess.call(protoc_args)
+    if ret != 0:
+      return ret
+  finally:
+    if options.use_system_protobuf == 1:
+      # Remove temporary directory holding re-written files.
+      shutil.rmtree(proto_path)
+
+  # protoc succeeded, check to see if the generated cpp header needs editing.
+  if not options.extra_header or not options.generated_header:
+    return 0
+  return ModifyHeader(options.generated_header, options.extra_header)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))

swarming_client @ b39a448d

+Subproject commit b39a448d8522392389b28f6997126a6ab04bfe87

tools/vim/clang-format.vim

+" Copyright (c) 2014 The Chromium Authors. All rights reserved.
+" Use of this source code is governed by a BSD-style license that can be
+" found in the LICENSE file.
+
+" Binds cmd-shift-i (on Mac) or ctrl-shift-i (elsewhere) to invoking
+" clang-format.py.
+" It will format the current selection (and if there's no selection, the
+" current line.)
+
+let s:script = expand('<sfile>:p:h') .
+  \'/../../buildtools/clang_format/script/clang-format.py'
+
+if has('mac')
+  execute "map <D-I> :pyf " . s:script . "<CR>"
+  execute "imap <D-I> <ESC>:pyf " . s:script . "<CR>i"
+else
+  execute "map <C-I> :pyf " . s:script . "<CR>"
+  execute "imap <C-I> <ESC>:pyf " . s:script . "<CR>i"
+endif

tools/vim/filetypes.vim

+" To get syntax highlighting and tab settings for gyp(i) and DEPS files,
+" add the following to your .vimrc file:
+"     so /path/to/src/tools/vim/filetypes.vim
+
+augroup filetype
+        au! BufRead,BufNewFile *.gyp    set filetype=python expandtab tabstop=2 shiftwidth=2
+        au! BufRead,BufNewFile *.gypi   set filetype=python expandtab tabstop=2 shiftwidth=2
+        au! BufRead,BufNewFile DEPS     set filetype=python expandtab tabstop=2 shiftwidth=2
+augroup END

tools/vim/mojom/ftdetect/mojomfiletype.vim

+" Copyright 2015 The Chromium Authors. All rights reserved.
+" Use of this source code is governed by a BSD-style license that can be
+" found in the LICENSE file.
+
+" We take care to preserve the user's fileencodings and fileformats,
+" because those settings are global (not buffer local), yet we want
+" to override them for loading mojom files, which should be UTF-8.
+
+let s:current_fileformats = ''
+let s:current_fileencodings = ''
+
+" define fileencodings to open as utf-8 encoding even if it's ascii.
+function! s:mojomfiletype_pre()
+  let s:current_fileformats = &g:fileformats
+  let s:current_fileencodings = &g:fileencodings
+  set fileencodings=utf-8 fileformats=unix
+  setlocal filetype=mojom
+endfunction
+
+" restore fileencodings as others
+function! s:mojomfiletype_post()
+  let &g:fileformats = s:current_fileformats
+  let &g:fileencodings = s:current_fileencodings
+endfunction
+
+au BufNewFile *.mojom setlocal filetype=mojom fileencoding=utf-8 fileformat=unix
+au BufRead *.mojom call s:mojomfiletype_pre()
+au BufReadPost *.mojom call s:mojomfiletype_post()

tools/vim/mojom/syntax/mojom.vim

+" Copyright 2015 The Chromium Authors. All rights reserved.
+" Use of this source code is governed by a BSD-style license that can be
+" found in the LICENSE file.
+
+" Vim syntax file " Language: Mojom
+" To get syntax highlighting for .mojom files, add the following to your .vimrc
+" file:
+"     set runtimepath^=/path/to/src/tools/vim/mojom
+
+syn case match
+
+syntax region mojomFold start="{" end="}" transparent fold
+
+" keyword definitions
+syntax keyword mojomType        bool int8 int16 int32 int64 uint8 uint16 uint32 uint64 float double array
+syntax match mojomImport        "^\(import\)\s"
+syntax keyword mojomKeyword     const module interface enum struct union
+syntax match mojomOperator      /=>/
+syntax match mojomOperator      /?/
+
+" Comments
+syntax keyword mojomTodo           contained TODO FIXME XXX
+syntax region  mojomComment        start="/\*"  end="\*/" contains=mojomTodo,mojomDocLink,@Spell
+syntax match   mojomLineComment    "//.*" contains=mojomTodo,@Spell
+syntax match   mojomLineDocComment "///.*" contains=mojomTodo,mojomDocLink,@Spell
+syntax region  mojomDocLink        contained start=+\[+ end=+\]+
+
+" Strings
+syn region mojomString start=+L\="+ skip=+\\\\\|\\"+ end=+"+ contains=@Spell
+hi def link mojomString            String
+
+" The default highlighting.
+highlight default link mojomTodo            Todo
+highlight default link mojomComment         Comment
+highlight default link mojomLineComment     Comment
+highlight default link mojomLineDocComment  Comment
+highlight default link mojomDocLink         SpecialComment
+highlight default link mojomType            Type
+highlight default link mojomImport          Include
+highlight default link mojomKeyword         Keyword
+highlight default link mojomOperator        Operator
+
+let b:current_syntax = "mojom"
+let b:spell_options = "contained"
+
+syn sync minlines=500
+
+let b:current_syntax = "mojom"

tools/vim/ninja-build.vim

+" Copyright (c) 2012 The Chromium Authors. All rights reserved.
+" Use of this source code is governed by a BSD-style license that can be
+" found in the LICENSE file.
+"
+" Adds a "Compile this file" function, using ninja. On Mac, binds Cmd-k to
+" this command. On Windows, Ctrl-F7 (which is the same as the VS default).
+" On Linux, <Leader>o, which is \o by default ("o"=creates .o files)
+"
+" Adds a "Build this target" function, using ninja. This is not bound
+" to any key by default, but can be used via the :CrBuild command.
+" It builds 'chrome' by default, but :CrBuild target1 target2 etc works as well.
+"
+" Requires that gyp has already generated build.ninja files, and that ninja is
+" in your path (which it is automatically if depot_tools is in your path).
+"
+" Add the following to your .vimrc file:
+"     so /path/to/src/tools/vim/ninja-build.vim
+
+python << endpython
+import os
+import vim
+
+
+def path_to_current_buffer():
+  """Returns the absolute path of the current buffer."""
+  return vim.current.buffer.name
+
+
+def path_to_source_root():
+  """Returns the absolute path to the chromium source root."""
+  candidate = os.path.dirname(path_to_current_buffer())
+  # This is a list of files that need to identify the src directory. The shorter
+  # it is, the more likely it's wrong (checking for just "build/common.gypi"
+  # would find "src/v8" for files below "src/v8", as "src/v8/build/common.gypi"
+  # exists). The longer it is, the more likely it is to break when we rename
+  # directories.
+  fingerprints = ['chrome', 'net', 'v8', 'build', 'skia']
+  while candidate and not all(
+      [os.path.isdir(os.path.join(candidate, fp)) for fp in fingerprints]):
+    candidate = os.path.dirname(candidate)
+  return candidate
+
+
+def path_to_build_dir(configuration):
+  """Returns <chrome_root>/<output_dir>/(Release|Debug)."""
+
+  chrome_root = path_to_source_root()
+  sys.path.append(os.path.join(chrome_root, 'tools', 'vim'))
+  from ninja_output import GetNinjaOutputDirectory
+  return GetNinjaOutputDirectory(chrome_root, configuration)
+
+def compute_ninja_command_for_current_buffer(configuration=None):
+  """Returns the shell command to compile the file in the current buffer."""
+  build_dir = path_to_build_dir(configuration)
+
+  # ninja needs filepaths for the ^ syntax to be relative to the
+  # build directory.
+  file_to_build = path_to_current_buffer()
+  file_to_build = os.path.relpath(file_to_build, build_dir)
+
+  build_cmd = ' '.join(['ninja', '-C', build_dir, file_to_build + '^'])
+  if sys.platform == 'win32':
+    # Escape \ for Vim, and ^ for both Vim and shell.
+    build_cmd = build_cmd.replace('\\', '\\\\').replace('^', '^^^^')
+  vim.command('return "%s"' % build_cmd)
+
+
+def compute_ninja_command_for_targets(targets='', configuration=None):
+  build_cmd = ' '.join(['ninja', '-C', path_to_build_dir(configuration),
+                        targets])
+  vim.command('return "%s"' % build_cmd)
+endpython
+
+fun! s:MakeWithCustomCommand(build_cmd)
+  let l:oldmakepgr = &makeprg
+  let &makeprg=a:build_cmd
+  if exists(':Make') == 2
+    Make
+  else
+    silent make | cwindow
+  endif
+  if !has('gui_running')
+    redraw!
+  endif
+  let &makeprg = l:oldmakepgr
+endfun
+
+fun! s:NinjaCommandForCurrentBuffer()
+  python compute_ninja_command_for_current_buffer()
+endfun
+
+fun! s:NinjaCommandForTargets(targets)
+  python compute_ninja_command_for_targets(vim.eval('a:targets'))
+endfun
+
+fun! CrCompileFile()
+  call s:MakeWithCustomCommand(s:NinjaCommandForCurrentBuffer())
+endfun
+
+fun! CrBuild(...)
+  let l:targets = a:0 > 0 ? join(a:000, ' ') : ''
+  if (l:targets !~ '\i')
+    let l:targets = 'chrome'
+  endif
+  call s:MakeWithCustomCommand(s:NinjaCommandForTargets(l:targets))
+endfun
+
+command! CrCompileFile call CrCompileFile()
+command! -nargs=* CrBuild call CrBuild(<q-args>)
+
+if has('mac')
+  map <D-k> :CrCompileFile<cr>
+  imap <D-k> <esc>:CrCompileFile<cr>
+elseif has('win32')
+  map <C-F7> :CrCompileFile<cr>
+  imap <C-F7> <esc>:CrCompileFile<cr>
+elseif has('unix')
+  map <Leader>o :CrCompileFile<cr>
+endif

tools/vim/ninja_output.py

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+import os
+import os.path
+import re
+
+
+def GetNinjaOutputDirectory(chrome_root, configuration=None):
+  """Returns <chrome_root>/<output_dir>/(Release|Debug).
+
+  The output_dir is detected in the following ways, in order of precedence:
+  1. CHROMIUM_OUT_DIR environment variable.
+  2. GYP_GENERATOR_FLAGS environment variable output_dir property.
+  3. Symlink target, if src/out is a symlink.
+  4. Most recently modified (e.g. built) directory called out or out_*.
+
+  The configuration chosen is the one most recently generated/built, but can be
+  overriden via the <configuration> parameter."""
+
+  output_dirs = []
+  if ('CHROMIUM_OUT_DIR' in os.environ and
+      os.path.isdir(os.path.join(chrome_root, os.environ['CHROMIUM_OUT_DIR']))):
+    output_dirs = [os.environ['CHROMIUM_OUT_DIR']]
+  if not output_dirs:
+    generator_flags = os.getenv('GYP_GENERATOR_FLAGS', '').split(' ')
+    for flag in generator_flags:
+      name_value = flag.split('=', 1)
+      if (len(name_value) == 2 and name_value[0] == 'output_dir' and
+          os.path.isdir(os.path.join(chrome_root, name_value[1]))):
+        output_dirs = [name_value[1]]
+  if not output_dirs:
+    out = os.path.join(chrome_root, 'out')
+    if os.path.islink(out):
+      out_target = os.path.join(os.path.dirname(out), os.readlink(out))
+      if os.path.exists(out_target):
+        output_dirs = [out_target]
+  if not output_dirs:
+    for f in os.listdir(chrome_root):
+      if (re.match('out(?:$|_)', f) and
+          os.path.isdir(os.path.join(chrome_root, f))):
+        output_dirs.append(f)
+
+  configs = [configuration] if configuration else ['Debug', 'Release']
+  output_paths = [os.path.join(chrome_root, out_dir, config)
+                  for out_dir in output_dirs for config in configs]
+
+  def approx_directory_mtime(path):
+    if not os.path.exists(path):
+      return -1
+    # This is a heuristic; don't recurse into subdirectories.
+    paths = [path] + [os.path.join(path, f) for f in os.listdir(path)]
+    return max(os.path.getmtime(p) for p in paths)
+
+  return max(output_paths, key=approx_directory_mtime)