Make ForwardingDisplayDelegate initially sync.

mojo/public/cpp/bindings/sync_call_restrictions.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_SYNC_CALL_RESTRICTIONS_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_SYNC_CALL_RESTRICTIONS_H_
 
 #include "base/macros.h"
 #include "base/threading/thread_restrictions.h"
 #include "mojo/public/cpp/bindings/bindings_export.h"
 
 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
 #define ENABLE_SYNC_CALL_RESTRICTIONS 1
 #else
 #define ENABLE_SYNC_CALL_RESTRICTIONS 0
 #endif
 
+namespace display {
+class ForwardingDisplayDelegate;
+}
+
 namespace leveldb {
 class LevelDBMojoProxy;
 }
 
 namespace prefs {
 class PersistentPrefStoreClient;
 }
 
 namespace ui {
 class Gpu;
@@ skipping 37 matching lines @@
   // Pref service connection is sync at startup.
   friend class prefs::PersistentPrefStoreClient;
 
   // END ALLOWED USAGE.
 
   // BEGIN USAGE THAT NEEDS TO BE FIXED.
   // In the non-mus case, we called blocking OS functions in the ui::Clipboard
   // implementation which weren't caught by sync call restrictions. Our blocking
   // calls to mus, however, are.
   friend class views::ClipboardMus;
+  // In ash::Shell::Init() it assumes that NativeDisplayDelegate will be
+  // synchronous at first. In mushrome ForwardingDisplayDelegate uses a
+  // synchronous call to get the display snapshots as a workaround.
+  friend class display::ForwardingDisplayDelegate;
   // END USAGE THAT NEEDS TO BE FIXED.
 
 #if ENABLE_SYNC_CALL_RESTRICTIONS
   static void IncreaseScopedAllowCount();
   static void DecreaseScopedAllowCount();
 #else
   static void IncreaseScopedAllowCount() {}
   static void DecreaseScopedAllowCount() {}
 #endif
 
@@ skipping 14 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowSyncCall);
   };
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(SyncCallRestrictions);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_SYNC_CALL_RESTRICTIONS_H_