Allow multiple logging::LogMessage{Handler,Listener}s

content/gpu/gpu_child_thread.h

Index: content/gpu/gpu_child_thread.h
diff --git a/content/gpu/gpu_child_thread.h b/content/gpu/gpu_child_thread.h
index 3e2b99e8b48e2f06e7be1d59e4ed0e3701de8bac..76cfcd5662ec5e53aebf49ee13d14df8d205b592 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -45,6 +45,16 @@ class TargetServices;
 }
 
 namespace content {
+class GpuProcessControlImpl;
+class GpuProcessLogMessageListener : logging::LogMessageListener {
+ public:
+  void OnMessage(int severity,
+                 const char* file,
+                 int line,
+                 size_t message_start,
+                 const std::string& str) override;
+};
+
 class GpuServiceFactory;
 struct EstablishChannelParams;
 
@@ -172,6 +182,8 @@ class GpuChildThread : public ChildThreadImpl,
   mojo::BindingSet<service_manager::mojom::ServiceFactory>
       service_factory_bindings_;
 
+  std::unique_ptr<GpuProcessLogMessageListener> log_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuChildThread);
 };