gpu: check GL_RGB565 work in ES3 context

gpu/command_buffer/service/feature_info.h

Index: gpu/command_buffer/service/feature_info.h
diff --git a/gpu/command_buffer/service/feature_info.h b/gpu/command_buffer/service/feature_info.h
index 9038ca8222977b6f9b223879ea10a7a0eb264368..c11e4bccff705af3cb5919e5b7a4925c87190c06 100644
--- a/gpu/command_buffer/service/feature_info.h
+++ b/gpu/command_buffer/service/feature_info.h
@@ -144,6 +144,7 @@ class GPU_EXPORT FeatureInfo : public base::RefCounted<FeatureInfo> {
 
   bool IsES3Capable() const;
   void EnableES3Validators();
+  void EnableES3ValidatorsForTesting();
 
   bool IsES3Enabled() const {
     return unsafe_es3_apis_enabled_;
@@ -190,6 +191,7 @@ class GPU_EXPORT FeatureInfo : public base::RefCounted<FeatureInfo> {
   bool enable_unsafe_es3_apis_switch_;
 
   bool unsafe_es3_apis_enabled_;
+  bool testing_es3_apis_enabled_ = false;
 
   bool ext_color_buffer_float_available_;
   bool oes_texture_float_linear_available_;