Teach GPU command buffer whether a context is webgl.

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 aac9d6036ed625f381a757b5ccffcc5cfeb33552..12b155145f602ae6a0d622b38cf63a502c3271f4 100644
--- a/gpu/command_buffer/common/gles2_cmd_utils.h
+++ b/gpu/command_buffer/common/gles2_cmd_utils.h
@@ -216,7 +216,8 @@ struct GLES2_UTILS_EXPORT ContextCreationAttribHelper {
   bool bind_generates_resource;
   bool fail_if_major_perf_caveat;
   bool lose_context_when_out_of_memory;
-  bool es3_context_required;
+  // 0 if not a WebGL context.
+  unsigned webgl_version;
 };
 
 }  // namespace gles2