Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/visual_state_browsertest.cc

 // Copyright 2015 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 "base/command_line.h"
 #include "base/run_loop.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/renderer/render_view.h"
@@ skipping 32 matching lines @@
                      commit_number, runner);
       quit_closures_.insert(&quit_closure);
       runner->Run();
       quit_closures_.erase(&quit_closure);
     }
   }
 
   int GetCommitCount() { return commit_count_; }
 
  private:
+  // RenderViewObserver implementation.
+  void OnDestruct() override { delete this; }
+
   std::set<base::Closure*> quit_closures_;
   int commit_count_;
 };
 
 class VisualStateTest : public ContentBrowserTest {
  public:
   VisualStateTest() : callback_count_(0) {}
 
   void SetUpCommandLine(base::CommandLine* command_line) override {
     command_line->AppendSwitch(switches::kSingleProcess);
@@ skipping 51 matching lines @@
   shell()->web_contents()->GetMainFrame()->InsertVisualStateCallback(base::Bind(
       &VisualStateTest::InvokeVisualStateCallback, base::Unretained(this)));
 
   // Verify that the callback is invoked and a new commit completed.
   PostTaskToInProcessRendererAndWait(base::Bind(
       &VisualStateTest::WaitForCommit, base::Unretained(this), &observer, 2));
   EXPECT_EQ(1, GetCallbackCount());
 }
 
 }  // namespace content