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 7eb8c4629f482049a007c183b2356e7e18973fff..6248086c4203e1bcd86c3709f02fa2058d121d53 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -45,6 +45,11 @@ 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 GpuWatchdogThread;
 struct EstablishChannelParams;
 
@@ -174,6 +179,8 @@ class GpuChildThread : public ChildThreadImpl,
   // Bindings to the mojom::ProcessControl impl.
   mojo::BindingSet<mojom::ProcessControl> process_control_bindings_;
 
+  std::unique_ptr<GpuProcessLogMessageListener> log_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuChildThread);
 };