Add command buffer support for EXT_sRGB_write_control

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 d4505cf92173dbd4ac18e2dbad9e2e21f15fddd1..e24cbdaa9076308296a910335321e14b4d07edf6 100644
--- a/gpu/command_buffer/service/context_state.h
+++ b/gpu/command_buffer/service/context_state.h
@@ -355,7 +355,11 @@ struct GPU_EXPORT ContextState {
 
   void InitStateManual(const ContextState* prev_state) const;
 
-  bool framebuffer_srgb_;
+  // EnableDisableFramebufferSRGB is called at very high frequency. Cache the
+  // true value of FRAMEBUFFER_SRGB, if we know it, to elide some of these
+  // calls.
+  bool framebuffer_srgb_valid_ = false;

[Zhenyao Mo, 2016/11/30 19:31:11]

This is nicer than the previous tracking mechanism

+  bool framebuffer_srgb_ = false;
 
   // Generic vertex attrib base types: FLOAT, INT, or UINT.
   // Each base type is encoded into 2 bits, the lowest 2 bits for location 0,