gpu: Remove unused GpuChildThread::gpu_preferences_.

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 70aace9fac776dfc74e0de1823d351f58d867312..0da6cd32618517e7842d53d7c45737786487e94a 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -64,8 +64,7 @@ class GpuChildThread : public ChildThreadImpl,
                  const DeferredMessages& deferred_messages,
                  gpu::GpuMemoryBufferFactory* gpu_memory_buffer_factory);
 
-  GpuChildThread(const gpu::GpuPreferences& gpu_preferences,
-                 const InProcessChildThreadParams& params,
+  GpuChildThread(const InProcessChildThreadParams& params,
                  gpu::GpuMemoryBufferFactory* gpu_memory_buffer_factory);
 
   ~GpuChildThread() override;
@@ -75,8 +74,6 @@ class GpuChildThread : public ChildThreadImpl,
   void Init(const base::Time& process_start_time);
   void StopWatchdog();
 
-  gpu::GpuPreferences gpu_preferences() { return gpu_preferences_; }
-
  private:
   // ChildThreadImpl:.
   bool Send(IPC::Message* msg) override;
@@ -132,8 +129,6 @@ class GpuChildThread : public ChildThreadImpl,
 
   void BindServiceFactoryRequest(shell::mojom::ServiceFactoryRequest request);
 
-  gpu::GpuPreferences gpu_preferences_;
-
   // Set this flag to true if a fatal error occurred before we receive the
   // OnInitialize message, in which case we just declare ourselves DOA.
   bool dead_on_arrival_;