Change ClipboardMus to use mojo::SyncCallRestrictions::ScopedAllowSyncCall.

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"
 
 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
 #define ENABLE_SYNC_CALL_RESTRICTIONS 1
 #else
 #define ENABLE_SYNC_CALL_RESTRICTIONS 0
 #endif
 
 namespace mus {
 class GpuService;
 }
 
+namespace views {
+class ClipboardMus;
+}
+
 namespace mojo {
 
 // In some processes, sync calls are disallowed. For example, in the browser
 // process we don't want any sync calls to child processes for performance,
 // security and stability reasons. SyncCallRestrictions helps to enforce such
 // rules.
 //
 // Before processing a sync call, the bindings call
 // SyncCallRestrictions::AssertSyncCallAllowed() to check whether sync calls are
 // allowed. By default, it is determined by the mojo system property
 // MOJO_PROPERTY_SYNC_CALL_ALLOWED. If the default setting says no but you have
 // a very compelling reason to disregard that (which should be very very rare),
 // you can override it by constructing a ScopedAllowSyncCall object, which
 // allows making sync calls on the current thread during its lifetime.
 class SyncCallRestrictions {
  public:
 #if ENABLE_SYNC_CALL_RESTRICTIONS
   // Checks whether the current thread is allowed to make sync calls, and causes
   // a DCHECK if not.
   static void AssertSyncCallAllowed();
 #else
   // Inline the empty definitions of functions so that they can be compiled out.
   static void AssertSyncCallAllowed() {}
 #endif
 
  private:
-// DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to mojo/OWNERS first.
-// BEGIN ALLOWED USAGE.
+  // 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.
+  // 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;
+  // 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
 
   // If a process is configured to disallow sync calls in general, constructing
@@ skipping 13 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowSyncCall);
   };
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(SyncCallRestrictions);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_SYNC_CALL_RESTRICTIONS_H_