Move TransferNavigationResourceThrottle into CrossSiteResourceHandler.

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 ffcc72b3b8dca97981cebe899e4becc36b3ac48b..624d36795c7b79a9ea9a78f8495663d2b049243a 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -113,34 +113,43 @@
 // a new RenderViewHost dedicated to the new SiteInstance.  This works as
 // follows:
 //
-// - Navigate determines whether the destination is cross-site, and if so,
+// - RVHM::Navigate determines whether the destination is cross-site, and if so,
 //   it creates a pending_render_view_host_.
 // - The pending RVH is "suspended," so that no navigation messages are sent to
-//   its renderer until the onbeforeunload JavaScript handler has a chance to
+//   its renderer until the beforeunload JavaScript handler has a chance to
 //   run in the current RVH.
 // - The pending RVH tells CrossSiteRequestManager (a thread-safe singleton)
-//   that it has a pending cross-site request.  ResourceDispatcherHost will
-//   check for this when the response arrives.
-// - The current RVH runs its onbeforeunload handler.  If it returns false, we
+//   that it has a pending cross-site request.  We will check this on the IO
+//   thread when deciding how to handle the response.
+// - The current RVH runs its beforeunload handler.  If it returns false, we
 //   cancel all the pending logic.  Otherwise we allow the pending RVH to send
 //   the navigation request to its renderer.
 // - ResourceDispatcherHost receives a ResourceRequest on the IO thread for the
-//   main resource load on the pending RVH. It checks CrossSiteRequestManager
-//   to see that it is a cross-site request, and installs a
-//   CrossSiteResourceHandler.
+//   main resource load on the pending RVH.  It creates a
+//   CrossSiteResourceHandler to check whether a process swap is needed when
+//   the request is ready to commit.
 // - When RDH receives a response, the BufferedResourceHandler determines
 //   whether it is a download.  If so, it sends a message to the new renderer
 //   causing it to cancel the request, and the download proceeds. For now, the
 //   pending RVH remains until the next DidNavigate event for this
 //   WebContentsImpl. This isn't ideal, but it doesn't affect any functionality.
 // - After RDH receives a response and determines that it is safe and not a
-//   download, it pauses the response to first run the old page's onunload
-//   handler.  It does this by asynchronously calling the OnCrossSiteResponse
-//   method of WebContentsImpl on the UI thread, which sends a SwapOut message
-//   to the current RVH.
-// - Once the onunload handler is finished, a SwapOut_ACK message is sent to
-//   the ResourceDispatcherHost, who unpauses the response.  Data is then sent
-//   to the pending RVH.
+//   download, the CrossSiteResourceHandler checks whether a process swap is
+//   needed (either because CrossSiteRequestManager has state for it or because
+//   a transfer was needed for a redirect).
+// - If so, CrossSiteResourceHandler pauses the response to first run the old
+//   page's unload handler.  It does this by asynchronously calling the
+//   OnCrossSiteResponse method of RenderViewHostManager on the UI thread, which
+//   sends a SwapOut message to the current RVH.
+// - Once the unload handler is finished, RVHM::SwappedOut checks if a transfer
+//   to a new process is needed, based on the stored pending_nav_params_.  (This
+//   is independent of whether we started out with a cross-process navigation.)
+//   - If not, it just tells the ResourceDispatcherHost to resume the response
+//     to its current RenderViewHost.
+//   - If so, it cancels the current pending RenderViewHost and sets up a new
+//     navigation using RequestTransferURL.  When the transferred request
+//     arrives in the ResourceDispatcherHost, we transfer the response and
+//     resume it.
 // - The pending renderer sends a FrameNavigate message that invokes the
 //   DidNavigate method.  This replaces the current RVH with the
 //   pending RVH.