Refactor GrGLUniformManager::UniformHandle to initialize itself by default

src/gpu/gl/GrGLUniformHandle.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrUniformHandle_DEFINED
 #define GrUniformHandle_DEFINED
 
-namespace {
-inline int handle_to_index(GrGLUniformManager::UniformHandle h) { return ~h; }
-inline GrGLUniformManager::UniformHandle index_to_handle(int i) { return ~i; }
+inline GrGLUniformManager::UniformHandle GrGLUniformManager::UniformHandle::CreateFromUniformIndex(int index) {
+    return GrGLUniformManager::UniformHandle(index);
 }
 
 #endif