Add GL_CHROMIUM_get_error_query

gpu/command_buffer/client/gles2_implementation.h

Index: gpu/command_buffer/client/gles2_implementation.h
diff --git a/gpu/command_buffer/client/gles2_implementation.h b/gpu/command_buffer/client/gles2_implementation.h
index bf6827393a04055b86b71d516d0480c938c14dfa..9b07a32f43a7a0c96627dc819c2845fa01bb78fe 100644
--- a/gpu/command_buffer/client/gles2_implementation.h
+++ b/gpu/command_buffer/client/gles2_implementation.h
@@ -198,9 +198,10 @@ class GLES2_IMPL_EXPORT GLES2Implementation {
 
   // The GLES2CmdHelper being used by this GLES2Implementation. You can use
   // this to issue cmds at a lower level for certain kinds of optimization.
-  GLES2CmdHelper* helper() const {
-    return helper_;
-  }
+  GLES2CmdHelper* helper() const;
+
+  // Gets client side generated errors.
+  GLenum GetClientSideGLError();
 
   // Include the auto-generated part of this class. We split this because
   // it means we can easily edit the non-auto generated parts right here in