gpu: Fix dependency cycle between service_sources and config_sources.

gpu/config/gpu_switches.h

Index: gpu/config/gpu_switches.h
diff --git a/chromecast/net/net_switches.h b/gpu/config/gpu_switches.h
similarity index 52%
copy from chromecast/net/net_switches.h
copy to gpu/config/gpu_switches.h
index dda9cac54fcd8ec8e8af35565fac0a3405cf1fc2..f6375ca06fe2ff30f23e40270c9f19dcb4d41668 100644
--- a/chromecast/net/net_switches.h
+++ b/gpu/config/gpu_switches.h
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROMECAST_NET_NET_SWITCHES_H_
-#define CHROMECAST_NET_NET_SWITCHES_H_
+#ifndef GPU_CONFIG_GPU_SWITCHES_H_
+#define GPU_CONFIG_GPU_SWITCHES_H_
+
+#include "gpu/gpu_export.h"
 
 namespace switches {
 
-extern const char kConnectivityCheckUrl[];
+GPU_EXPORT extern const char kGpuDriverBugWorkarounds[];
 
 }  // namespace switches
 
-#endif  // CHROMECAST_NET_NET_SWITCHES_H_
+#endif  // GPU_CONFIG_GPU_SWITCHES_H_