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 72e4c6c2442d7ffc3129cf47445e7899e296c129..6566974e62094c5de02adae530e0d827eb5a8279 100644
--- a/gpu/command_buffer/service/context_state.h
+++ b/gpu/command_buffer/service/context_state.h
@@ -354,7 +354,11 @@ 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;
+  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,