Disable FRAMEBUFFER_SRGB when restoring from a null context state

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 2378eeb3906693caec6f0b98b451a2b5eeedc1c9..7c53a72ba78dc23acdac519c8974dfb204e9a0a1 100644
--- a/gpu/command_buffer/service/context_state.h
+++ b/gpu/command_buffer/service/context_state.h
@@ -153,6 +153,12 @@ GPU_EXPORT void Vec4::SetValues<GLint>(const GLint* values);
 template <>
 GPU_EXPORT void Vec4::SetValues<GLuint>(const GLuint* values);
 
+enum FramebufferSRGBState {
+  FRAMEBUFFER_SRGB_UNDEFINED,
+  FRAMEBUFFER_SRGB_DISABLED,
+  FRAMEBUFFER_SRGB_ENABLED
+};
+
 struct GPU_EXPORT ContextState {
   enum Dimension {
     k2D,
@@ -272,7 +278,7 @@ struct GPU_EXPORT ContextState {
   PixelStoreParams GetPackParams();
   PixelStoreParams GetUnpackParams(Dimension dimension);
 
-  void EnableDisableFramebufferSRGB(bool enable);
+  void EnableDisableFramebufferSRGB(FramebufferSRGBState enable);
 
   #include "gpu/command_buffer/service/context_state_autogen.h"
 
@@ -341,7 +347,7 @@ struct GPU_EXPORT ContextState {
 
   void InitStateManual(const ContextState* prev_state) const;
 
-  bool framebuffer_srgb_;
+  FramebufferSRGBState framebuffer_srgb_;
 
   // Generic vertex attrib base types: FLOAT, INT, or UINT.
   // Each base type is encoded into 2 bits, the lowest 2 bits for location 0,