Destroy WebWidgetTestClient when its WebWidget is destroyed.

components/test_runner/web_test_proxy.h

 // 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.
 
 #ifndef COMPONENTS_TEST_RUNNER_WEB_TEST_PROXY_H_
 #define COMPONENTS_TEST_RUNNER_WEB_TEST_PROXY_H_
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 41 matching lines @@
 
 // WebTestProxyBase is the "brain" of WebTestProxy in the sense that
 // WebTestProxy does the bridge between RenderViewImpl and WebTestProxyBase and
 // when it requires a behavior to be different from the usual, it will call
 // WebTestProxyBase that implements the expected behavior.
 // See WebTestProxy class comments for more information.
 class TEST_RUNNER_EXPORT WebTestProxyBase {
  public:
   blink::WebWidget* web_widget() { return web_widget_; }
   void set_web_widget(blink::WebWidget* widget) {
-    DCHECK(widget);
-    DCHECK(!web_widget_);
     web_widget_ = widget;
   }
 
   blink::WebView* web_view() { return web_view_; }
   void set_web_view(blink::WebView* view) {
     DCHECK(view);
     DCHECK(!web_view_);
     web_view_ = view;
   }
 
   void set_view_test_client(
       std::unique_ptr<WebViewTestClient> view_test_client) {
     DCHECK(view_test_client);
     DCHECK(!view_test_client_);
     view_test_client_ = std::move(view_test_client);
   }
 
   void set_widget_test_client(
       std::unique_ptr<WebWidgetTestClient> widget_test_client) {
-    DCHECK(widget_test_client);
-    DCHECK(!widget_test_client_);

[Łukasz Anforowicz, 2016/05/10 19:44:40]

This doesn't seem right - WebTestProxy dereferences widget_test_client without
any null checks (i.e. in screenInfo, scheduleAnimation, requestPointerLock
methods).

     widget_test_client_ = std::move(widget_test_client);
   }
 
   WebTestDelegate* delegate() { return delegate_; }
   void set_delegate(WebTestDelegate* delegate) {
     DCHECK(delegate);
     DCHECK(!delegate_);
     delegate_ = delegate;
   }
 
@@ skipping 156 matching lines @@
 
  private:
   virtual ~WebTestProxy() {}
 
   DISALLOW_COPY_AND_ASSIGN(WebTestProxy);
 };
 
 }  // namespace test_runner
 
 #endif  // COMPONENTS_TEST_RUNNER_WEB_TEST_PROXY_H_