Add EncodeBackbufferCHROMIUM support to GLES2 command stream

gpu/command_buffer/client/gles2_cmd_helper_autogen.h

Index: gpu/command_buffer/client/gles2_cmd_helper_autogen.h
diff --git a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
index d55fe341be704213787d5c58dca5a706fb037565..5d2de4c068983b2a26b988e30f48fddc00f0b30c 100644
--- a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
+++ b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
@@ -2100,5 +2100,13 @@
     }
   }
 
+  void EncodeBackbufferCHROMIUM() {
+    gles2::cmds::EncodeBackbufferCHROMIUM* c =
+        GetCmdSpace<gles2::cmds::EncodeBackbufferCHROMIUM>();
+    if (c) {
+      c->Init();
+    }
+  }
+
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_CMD_HELPER_AUTOGEN_H_