ui: Add libsync GLFence implementation.

ui/gfx/shared_event.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 UI_GFX_SHARED_EVENT_H_
 #define UI_GFX_SHARED_EVENT_H_
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process_handle.h"
 #include "base/time/time.h"
@@ skipping 12 matching lines @@
 
   // Create a new SharedEvent object from an existing, platform-specific
   // OS primitive.
   explicit SharedEvent(const SharedEventHandle& handle);
 
   // Creates a new event which can be used in a remote process. Returns a
   // platform-specific OS primitive for the new event. The caller is
   // responsible for destroying the OS primitive.
   static SharedEventHandle CreateForProcess(base::ProcessHandle process);
 
+  // Return true iff the given handle is valid (i.e. not the distingished
+  // invalid value; NULL for a HANDLE and -1 for a file descriptor)
+  static bool IsHandleValid(const SharedEventHandle& handle);
+
   // Duplicates the underlying OS primitive. The caller is responsible for
   // destroying the duplicated OS primitive.
   static SharedEventHandle DuplicateHandle(const SharedEventHandle& handle);
 
   // Put the event in the un-signaled state.
   void Reset();
 
   // Put the event in the signaled state. Causing any thread blocked on Wait
   // to be woken up.
   void Signal();
@@ skipping 20 matching lines @@
     return reinterpret_cast<int32_t*>(shared_memory_.memory());
   }
   base::SharedMemory shared_memory_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedEvent);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_SHARED_EVENT_H_