overscroll: Take a screenshot at more appropriate times.

content/browser/web_contents/web_contents_impl.cc

 // 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.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 2670 matching lines @@
 }
 
 void WebContentsImpl::RenderViewDeleted(RenderViewHost* rvh) {
   render_manager_.RenderViewDeleted(rvh);
   FOR_EACH_OBSERVER(WebContentsObserver, observers_, RenderViewDeleted(rvh));
 }
 
 void WebContentsImpl::DidNavigate(
     RenderViewHost* rvh,
     const ViewHostMsg_FrameNavigate_Params& params) {
-  if (PageTransitionIsMainFrame(params.transition))
+  if (PageTransitionIsMainFrame(params.transition)) {
+    // When overscroll navigation gesture is enabled, a screenshot of the page
+    // in its current state is taken so that it can be used during the
+    // nav-gesture. It is necessary to take the screenshot here, before calling
+    // RenderViewHostManager::DidNavigateMainFrame, because that can change
+    // WebContents::GetRenderViewHost to return the new host, instead of the one
+    // that may have just been swapped out.
+    controller_.TakeScreenshot();
+
     render_manager_.DidNavigateMainFrame(rvh);
+  }
 
   // Update the site of the SiteInstance if it doesn't have one yet, unless
   // this is for about:blank.  In that case, the SiteInstance can still be
   // considered unused until a navigation to a real page.
   if (!static_cast<SiteInstanceImpl*>(GetSiteInstance())->HasSite() &&
       params.url != GURL(chrome::kAboutBlankURL)) {
     static_cast<SiteInstanceImpl*>(GetSiteInstance())->SetSite(params.url);
   }
 
   // Need to update MIME type here because it's referred to in
@@ skipping 693 matching lines @@
 
 BrowserPluginGuest* WebContentsImpl::GetBrowserPluginGuest() {
   return browser_plugin_guest_.get();
 }
 
 BrowserPluginEmbedder* WebContentsImpl::GetBrowserPluginEmbedder() {
   return browser_plugin_embedder_.get();
 }
 
 }  // namespace content