Add a mechanism for command buffer to conditionally allow ES3 enums.

gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h

Index: gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
diff --git a/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h b/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
index 5512be9508255f6f6cfa560498e0b245eba2a503..11d849276e8773349192dbffa6d06a562307e6e2 100644
--- a/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
+++ b/gpu/command_buffer/service/gles2_cmd_validation_implementation_autogen.h
@@ -43,6 +43,15 @@ static const GLenum valid_buffer_target_table[] = {
     GL_ELEMENT_ARRAY_BUFFER,
 };
 
+static const GLenum valid_buffer_target_table_es3[] = {
+    GL_COPY_READ_BUFFER,
+    GL_COPY_WRITE_BUFFER,
+    GL_PIXEL_PACK_BUFFER,
+    GL_PIXEL_UNPACK_BUFFER,
+    GL_TRANSFORM_FEEDBACK_BUFFER,
+    GL_UNIFORM_BUFFER,
+};
+
 static const GLenum valid_buffer_usage_table[] = {
     GL_STREAM_DRAW,
     GL_STATIC_DRAW,
@@ -751,4 +760,9 @@ Validators::Validators()
                      arraysize(valid_vertex_pointer_table)) {
 }
 
+void Validators::AddES3Values() {
+  buffer_target.AddValues(valid_buffer_target_table_es3,
+                          arraysize(valid_buffer_target_table_es3));
+}
+
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_VALIDATION_IMPLEMENTATION_AUTOGEN_H_