Destroy the old RenderWidgetHostView when swapping out a main frame.

content/public/test/test_renderer_host.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_TEST_TEST_RENDERER_HOST_H_
 #define CONTENT_PUBLIC_TEST_TEST_RENDERER_HOST_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 157 matching lines @@
 };
 
 // You can instantiate only one class like this at a time.  During its
 // lifetime, RenderViewHost and RenderFrameHost objects created may be used via
 // RenderViewHostTester and RenderFrameHostTester respectively.
 class RenderViewHostTestEnabler {
  public:
   RenderViewHostTestEnabler();
   ~RenderViewHostTestEnabler();
 
+  void SetUp();

[Charlie Reis, 2016/11/29 19:35:55]

This needs a comment.  Lots of classes instantiate one of these (e.g.,
ExtensionEventObserverTest), but it doesn't look like you call SetUp in all of
them?  Why not?

+  void TearDown();
+
  private:
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostTestEnabler);
   friend class RenderViewHostTestHarness;
 
+#if defined(OS_ANDROID)
+  std::unique_ptr<MockGpuChannelEstablishFactory> gpu_channel_factory_;
+  std::unique_ptr<display::Screen> screen_;
+#endif
   std::unique_ptr<MockRenderProcessHostFactory> rph_factory_;
   std::unique_ptr<TestRenderViewHostFactory> rvh_factory_;
   std::unique_ptr<TestRenderFrameHostFactory> rfh_factory_;
 };
 
 // RenderViewHostTestHarness ---------------------------------------------------
 class RenderViewHostTestHarness : public testing::Test {
  public:
   RenderViewHostTestHarness();
   ~RenderViewHostTestHarness() override;
@@ skipping 81 matching lines @@
 
   std::unique_ptr<BrowserContext> browser_context_;
 
   std::unique_ptr<WebContents> contents_;
 #if defined(OS_WIN)
   std::unique_ptr<ui::ScopedOleInitializer> ole_initializer_;
 #endif
 #if defined(USE_AURA)
   std::unique_ptr<aura::test::AuraTestHelper> aura_test_helper_;
 #endif
-#if defined(OS_ANDROID)
-  std::unique_ptr<MockGpuChannelEstablishFactory> gpu_channel_factory_;
-  std::unique_ptr<display::Screen> screen_;
-#endif
   RenderViewHostTestEnabler rvh_test_enabler_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostTestHarness);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_TEST_RENDERER_HOST_H_