Enable creation of offscreen contexts which own their backing surface.

gpu/command_buffer/common/gles2_cmd_utils.h

Index: gpu/command_buffer/common/gles2_cmd_utils.h
diff --git a/gpu/command_buffer/common/gles2_cmd_utils.h b/gpu/command_buffer/common/gles2_cmd_utils.h
index 8d0f16baba0fa205bdfa407f56a41ed171c6cd35..1df70feeb50bd92e13dd91078e433003f165b16d 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.h
+++ b/gpu/command_buffer/common/gles2_cmd_utils.h
@@ -328,6 +328,8 @@ struct GLES2_UTILS_EXPORT ContextCreationAttribHelper {
   bool fail_if_major_perf_caveat;
   bool lose_context_when_out_of_memory;
   bool should_use_native_gmb_for_backbuffer;
+  bool own_offscreen_surface;
+  bool low_priority;
 
   ContextType context_type;
 };
@@ -336,4 +338,3 @@ struct GLES2_UTILS_EXPORT ContextCreationAttribHelper {
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_UTILS_H_
-