Jpeg invalid step by 2

BUG=210
TESTED=out\release\libyuv_unittest --gtest_filter=*J*
Review URL: https://webrtc-codereview.appspot.com/1276005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@632 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 631
+Version: 632
 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 631
+#define LIBYUV_VERSION 632
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/mjpeg_decoder.cc

@@ -86,10 +86,14 @@ bool ValidateJpeg(const uint8* sample, size_t sample_size) {
     // ERROR: Invalid jpeg initial start code
     return false;
   }
-  for (int i = static_cast<int>(sample_size) - 1; i > 2; --i) {
-    if (sample[i - 1] == 0xff && sample[i] == 0xd9) {  // End Of Image
+  for (int i = static_cast<int>(sample_size) - 2; i > 1;) {
+    if (sample[i] != 0xd9) {
+      if (sample[i] == 0xff && sample[i + 1] == 0xd9) {  // End Of Image
         return true;
       }
+      --i;
+    }
+    --i;
   }
   // ERROR: Invalid jpeg end code not found. Size sample_size
   return false;