overscroll: Take a screenshot at more appropriate times.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 6a058992ed111bc6d71edef0003a64b7ee316a91..3891060099e14b58c176d7c2f15bfc24d49011b2 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -2688,8 +2688,17 @@ void WebContentsImpl::RenderViewDeleted(RenderViewHost* 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