Implement helper functionalities for computing image size with ES3 settings.

gpu/command_buffer/service/context_state.h

Index: gpu/command_buffer/service/context_state.h
diff --git a/gpu/command_buffer/service/context_state.h b/gpu/command_buffer/service/context_state.h
index 5f154c28a73eb90bcec864f3cee7399585da8f1e..e1fa4a4bb3c33d5f0f4cca98af2eb4727018ccc5 100644
--- a/gpu/command_buffer/service/context_state.h
+++ b/gpu/command_buffer/service/context_state.h
@@ -138,6 +138,11 @@ template <>
 GPU_EXPORT void Vec4::SetValues<GLuint>(const GLuint* values);
 
 struct GPU_EXPORT ContextState {
+  enum Dimension {
+    k2D,
+    k3D
+  };
+
   ContextState(FeatureInfo* feature_info,
                ErrorStateClient* error_state_client,
                Logger* logger);
@@ -220,6 +225,9 @@ struct GPU_EXPORT ContextState {
   void UnbindTexture(TextureRef* texture);
   void UnbindSampler(Sampler* sampler);
 
+  PixelStoreParams GetPackParams();
+  PixelStoreParams GetUnpackParams(Dimension dimension);
+
   #include "gpu/command_buffer/service/context_state_autogen.h"
 
   EnableFlags enable_flags;