Use GpuPreferences to avoid directly accessing switches in gpu related code

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 7cbe0fa6f1c781b72c6607fea76cb8c73333dc24..2bfeef19f2be73f51f44bd55a6299a3401365212 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -23,6 +23,7 @@
 #include "content/common/gpu/gpu_config.h"
 #include "content/common/gpu/x_util.h"
 #include "content/common/process_control.mojom.h"
+#include "gpu/command_buffer/service/gpu_preferences.h"
 #include "gpu/config/gpu_info.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
@@ -68,12 +69,14 @@ class GpuChildThread : public ChildThreadImpl,
   void Init(const base::Time& process_start_time);
   void StopWatchdog();
 
+ private:
+  void InitGpuPreferences();
+
   // ChildThread overrides.
   bool Send(IPC::Message* msg) override;
   bool OnControlMessageReceived(const IPC::Message& msg) override;
   bool OnMessageReceived(const IPC::Message& msg) override;
 
- private:
   // GpuChannelManagerDelegate implementation.
   void AddSubscription(int32_t client_id, unsigned int target) override;
   void ChannelEstablished(const IPC::ChannelHandle& channel_handle) override;
@@ -131,6 +134,8 @@ class GpuChildThread : public ChildThreadImpl,
   void BindProcessControlRequest(
       mojo::InterfaceRequest<ProcessControl> 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_;