Fix the issue that it may get wrong stride in cc::ResourceProvider::MapImage.

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index 348516da7ddae34b11eace46c45a6251dfb2f221..05bb9d71697e9a0d9ff0b7340c45b4d400310258 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -3908,6 +3908,10 @@ void GLES2Implementation::GetImageParameterivCHROMIUMHelper(
     return;
   }
 
+  // In Android, the SurfaceTexture based GpuMemoryBuffer can only get the
+  // exact stride after it is mapped. Here it would be better to ensure that
+  // it maps image first and then calls GetStride().

[reveman, 2014/03/03 16:57:48]

Same thing here. I would prefer no platform/implementation specific details
here.

Actually, I think this should generate a GL_INVALID_OPERATION instead of a
DCHECK failure as it's not an implementation detail but part of the spec.

[junj, 2014/03/04 11:11:23]

Done.

+  DCHECK(gpu_buffer->IsMapped());
   *params = gpu_buffer->GetStride();
 }