Check BrowsingInstance before swapping prerenders.

content/browser/frame_host/render_frame_host_manager_unittest.cc

Index: content/browser/frame_host/render_frame_host_manager_unittest.cc
diff --git a/content/browser/frame_host/render_frame_host_manager_unittest.cc b/content/browser/frame_host/render_frame_host_manager_unittest.cc
index c0afa6718885eef93b86cdd0888ecee92c5869bc..8e44208c5d5f841e91a5c585e5f55e166ba27f5a 100644
--- a/content/browser/frame_host/render_frame_host_manager_unittest.cc
+++ b/content/browser/frame_host/render_frame_host_manager_unittest.cc
@@ -1049,6 +1049,14 @@ TEST_F(RenderFrameHostManagerTest, WebUI) {
                             false /* is_renderer_init */);
   RenderFrameHostImpl* host = manager->Navigate(entry);
 
+  // This test creates a second FrameTree for the WebContents which throws off
+  // some of the accounting. This inverts what was done in
+  // WebContentsImpl::NotifySwapped.
+  static_cast<SiteInstanceImpl*>(instance)->
+      IncrementRelatedActiveContentsCount();
+  static_cast<SiteInstanceImpl*>(host->GetSiteInstance())->
+      DecrementRelatedActiveContentsCount();
+
   // We commit the pending RenderFrameHost immediately because the previous
   // RenderFrameHost was not live.  We test a case where it is live in
   // WebUIInNewTab.
@@ -1115,6 +1123,14 @@ TEST_F(RenderFrameHostManagerTest, WebUIInNewTab) {
   EXPECT_TRUE(
       host1->render_view_host()->GetEnabledBindings() & BINDINGS_POLICY_WEB_UI);
 
+  // This test creates a second FrameTree for the WebContents which throws off
+  // some of the accounting. This inverts what was done in
+  // WebContentsImpl::NotifySwapped.
+  static_cast<SiteInstanceImpl*>(blank_instance)->
+      IncrementRelatedActiveContentsCount();
+  static_cast<SiteInstanceImpl*>(host1->GetSiteInstance())->
+      DecrementRelatedActiveContentsCount();
+
   // Now simulate clicking a link that opens in a new tab.
   scoped_ptr<TestWebContents> web_contents2(
       TestWebContents::Create(browser_context(), webui_instance));