Fix autoroller in accordance to upstream change

This change broke libyuv's presubmit: https://chromium.googlesource.com/chromium/tools/depot_tools/+/e79ddeaabf246769937282f952897bcec3e9de05%5E%21/
GClientKeywords has been removed and replaced with a more direct substitution.
This is similar to https://codereview.webrtc.org/2989603002

BUG=None
NOTRY=True
TBR=fbarchard@google.com

Change-Id: I5cb1c18bc72ac1354d5d69f3c9f93cc61841c409
Reviewed-on: https://chromium-review.googlesource.com/615161Reviewed-by: Henrik Kjellander <kjellander@chromium.org>
Commit-Queue: Henrik Kjellander <kjellander@chromium.org>

tools_libyuv/autoroller/roll_deps.py

@@ -48,7 +48,6 @@ CHECKOUT_ROOT_DIR = os.path.realpath(os.path.join(CHECKOUT_SRC_DIR, os.pardir))
 sys.path.append(os.path.join(CHECKOUT_SRC_DIR, 'build'))
 import find_depot_tools
 find_depot_tools.add_depot_tools_to_path()
-from gclient import GClientKeywords
 
 CLANG_UPDATE_SCRIPT_URL_PATH = 'tools/clang/scripts/update.py'
 CLANG_UPDATE_SCRIPT_LOCAL_PATH = os.path.join(CHECKOUT_SRC_DIR, 'tools',
@@ -62,12 +61,14 @@ class RollError(Exception):
   pass
 
 
+def VarLookup(local_scope):
+  return lambda var_name: local_scope['vars'][var_name]
+
+
 def ParseDepsDict(deps_content):
   local_scope = {}
-  var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
-    'Var': var.Lookup,
+    'Var': VarLookup(local_scope),
     'deps_os': {},
   }
   exec(deps_content, global_scope, local_scope)

tools_libyuv/autoroller/unittests/roll_deps_test.py

@@ -82,6 +82,11 @@ class TestRollChromiumRevision(unittest.TestCase):
     self.assertEqual(self.fake.expectations, [])
     setattr(roll_deps, '_RunCommand', self.old_RunCommand)
 
+  def testVarLookup(self):
+    local_scope = {'foo': 'wrong', 'vars': {'foo': 'bar'}}
+    lookup = roll_deps.VarLookup(local_scope)
+    self.assertEquals(lookup('foo'), 'bar')
+
   def testUpdateDepsFile(self):
     new_rev = 'aaaaabbbbbcccccdddddeeeeefffff0000011111'