Use GpuPreferences to avoid directly accessing switches in gpu related code

gpu/command_buffer/service/mailbox_manager.h

Index: gpu/command_buffer/service/mailbox_manager.h
diff --git a/gpu/command_buffer/service/mailbox_manager.h b/gpu/command_buffer/service/mailbox_manager.h
index dd6dd73fbc56bfdbd3ede3d72f9437cde93446f3..d46dafd11efaf6f8f19f51d8c75530af63ad68ed 100644
--- a/gpu/command_buffer/service/mailbox_manager.h
+++ b/gpu/command_buffer/service/mailbox_manager.h
@@ -12,6 +12,7 @@
 
 namespace gpu {
 
+struct GpuPreferences;
 struct SyncToken;
 
 namespace gles2 {
@@ -21,7 +22,8 @@ class Texture;
 // Manages resources scoped beyond the context or context group level.
 class GPU_EXPORT MailboxManager : public base::RefCounted<MailboxManager> {
  public:
-  static scoped_refptr<MailboxManager> Create();
+  static scoped_refptr<MailboxManager> Create(
+      const GpuPreferences& gpu_preferences);
 
   // Look up the texture definition from the named mailbox.
   virtual Texture* ConsumeTexture(const Mailbox& mailbox) = 0;