Destroy the old RenderWidgetHostView when swapping out a main frame.

chrome/test/base/browser_with_test_window_test.cc

Index: chrome/test/base/browser_with_test_window_test.cc
diff --git a/chrome/test/base/browser_with_test_window_test.cc b/chrome/test/base/browser_with_test_window_test.cc
index c51adca39d72f02ba11c5a48617768a69b543414..3c71f67d61aa8a99e2d91429bfc17f333e566a56 100644
--- a/chrome/test/base/browser_with_test_window_test.cc
+++ b/chrome/test/base/browser_with_test_window_test.cc
@@ -81,6 +81,8 @@ void BrowserWithTestWindowTest::SetUp() {
 
   browser_.reset(
       CreateBrowser(profile(), browser_type_, hosted_app_, window_.get()));
+
+  rvh_test_enabler_.SetUp();
 }
 
 void BrowserWithTestWindowTest::TearDown() {
@@ -105,6 +107,8 @@ void BrowserWithTestWindowTest::TearDown() {
   views_test_helper_.reset();
 #endif
 
+  rvh_test_enabler_.TearDown();
+
   testing::Test::TearDown();
 
   // A Task is leaked if we don't destroy everything, then run the message