Add AsyncFlush when transferbuffer is > a certain size

gpu/command_buffer/client/gles2_implementation.h

Index: gpu/command_buffer/client/gles2_implementation.h
diff --git a/gpu/command_buffer/client/gles2_implementation.h b/gpu/command_buffer/client/gles2_implementation.h
index d8adc44f50e882079040bd699f784d08d22040b9..97622eac5cb11e0713596a438cc5ac122c505435 100644
--- a/gpu/command_buffer/client/gles2_implementation.h
+++ b/gpu/command_buffer/client/gles2_implementation.h
@@ -143,6 +143,9 @@ class GLES2Implementation {
   // used for testing only. If more things are reseved add them here.
   static const unsigned int kStartingOffset = kMaxSizeOfSimpleResult;
 
+  // Size in bytes to issue async flush for transfer buffer.
+  static const unsigned int kSizeToFlush = 256 * 1024;
+
   // The bucket used for results. Public for testing only.
   static const uint32 kResultBucketId = 1;