mus::GpuService: Support establish GpuChannel asynchronously.

mojo/public/cpp/bindings/sync_call_restrictions.h

Index: mojo/public/cpp/bindings/sync_call_restrictions.h
diff --git a/mojo/public/cpp/bindings/sync_call_restrictions.h b/mojo/public/cpp/bindings/sync_call_restrictions.h
index 78c1b7f3b9d2050d834fd3cbb3d03075206b779f..661deee341b6af42ba6c77c1135e1e23f1b9cb87 100644
--- a/mojo/public/cpp/bindings/sync_call_restrictions.h
+++ b/mojo/public/cpp/bindings/sync_call_restrictions.h
@@ -14,10 +14,6 @@
 #define ENABLE_SYNC_CALL_RESTRICTIONS 0
 #endif
 
-namespace mus {
-class GpuService;
-}
-
 namespace views {
 class ClipboardMus;
 }
@@ -50,7 +46,6 @@ class SyncCallRestrictions {
  private:
   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to mojo/OWNERS first.
   // BEGIN ALLOWED USAGE.
-  friend class mus::GpuService;  // http://crbug.com/620058
   // END ALLOWED USAGE.
 
   // BEGIN USAGE THAT NEEDS TO BE FIXED.