[ios] Purge web view if external app URL is current in navigation stack.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 6c926c06c7b6927f29403a948152e5f75f48c778..cc6865af9ee0fb149440c97f39f54f93329057f5 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -3343,6 +3343,17 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
     if ([self isMainFrameNavigationAction:action])
       [self stopLoading];
 
+    // Purge web view in case if last committed URL is different from the

[Jackie Quinn, 2016/08/08 21:30:09]

You could remove "in case"

[Eugene But (OOO till 7-30), 2016/08/08 21:47:31]

Done.

+    // document URL. This can happen if external URL was added to the navigation
+    // stack and was loaded using Go Back or Go Forward navigation (in which
+    // case document URL will point to the previous page).
+    GURL lastCommittedURL =
+        self.webState->GetNavigationManager()->GetLastCommittedItem()->GetURL();
+    if (lastCommittedURL != _documentURL) {
+      [self requirePageReconstruction];
+      _documentURL = lastCommittedURL;

[Jackie Quinn, 2016/08/08 21:30:09]

Is this something that generally needs to be done when there's a page
reconstruction? 

It looks like the header comments for requirePageReconstruction and friends are
littered with TODO(stuartmorgan): Clean up and consolidate. Is this on the web
tasks list? If not it probably should be?

[Eugene But (OOO till 7-30), 2016/08/08 21:47:31]

No, it's a special case where _documentURL does not represent the reality but it
should.
 
Yes, we have a list of various refactoring we need to do in web controller.

+    }
+
     if ([_delegate openExternalURL:requestURL
                        linkClicked:isNavigationTypeLinkActivated]) {
       // Record the URL so that errors reported following the 'NO' reply can be