Expose GpuMemoryBufferId through glGetImageivCHROMIUM.

gpu/gles2_conform_support/egl/context.h

Index: gpu/gles2_conform_support/egl/context.h
diff --git a/gpu/gles2_conform_support/egl/context.h b/gpu/gles2_conform_support/egl/context.h
index 341b5c0658d822e9a04e5d929cfccfd2301cac2d..bc3ad75fb1791b5ee79a26ca240370662e7351ae 100644
--- a/gpu/gles2_conform_support/egl/context.h
+++ b/gpu/gles2_conform_support/egl/context.h
@@ -68,6 +68,7 @@ class Context : public base::RefCountedThreadSafe<Context>,
                                      size_t height,
                                      unsigned internalformat,
                                      unsigned usage) override;
+  int32_t GetImageGpuMemoryBufferId(unsigned image_id) override;
   void SignalQuery(uint32_t query, const base::Closure& callback) override;
   void SetLock(base::Lock*) override;
   void EnsureWorkVisible() override;