InvokeCallbackTask should use UniquePersistent to hold callback.

content/shell/renderer/test_runner/test_runner.cc

 // Copyright 2014 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.
 
 #include "content/shell/renderer/test_runner/test_runner.h"
 
 #include <limits>
 
 #include "base/logging.h"
 #include "content/shell/common/test_runner/test_preferences.h"
@@ skipping 86 matching lines @@
     v8::Context::Scope context_scope(context);
 
     frame->callFunctionEvenIfScriptDisabled(
         v8::Local<v8::Function>::New(isolate, callback_),
         context->Global(),
         0,
         NULL);
   }
 
  private:
-  v8::Persistent<v8::Function> callback_;
+  v8::UniquePersistent<v8::Function> callback_;
 };
 
 class TestRunnerBindings : public gin::Wrappable<TestRunnerBindings> {
  public:
   static gin::WrapperInfo kWrapperInfo;
 
   static void Install(base::WeakPtr<TestRunner> controller,
                       WebFrame* frame);
 
  private:
@@ skipping 2529 matching lines @@
 }
 
 void TestRunner::DidLosePointerLockInternal() {
   bool was_locked = pointer_locked_;
   pointer_locked_ = false;
   if (was_locked)
     web_view_->didLosePointerLock();
 }
 
 }  // namespace content