[ios] Stop using the popstate event as speculative WebKit crash workaround.

Moving from the popstate event to a zero second setInterval shortens
session restoration by a few milliseconds, and perhaps works around the
iOS12.2+ crash.

Bug: 959499
Change-Id: Ic67a3cb146a9b3525efb6baa9dafae8e6bbf4ee1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1602873Reviewed-by: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Ali Juma <ajuma@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658282}

ios/web/navigation/resources/restore_session.html

@@ -46,15 +46,6 @@
       }
     };
 
-    /**
-     * The window.onpopstate event fires when the user navigates to one of the
-     * history entries created by restoreSession(). This handler forces a reload
-     * to reidrect to the target URL.
-     */
-    window.onpopstate = function(event) {
-      location.reload();
-    }
-
     /**
      * Manipulates the current session history to mimic the provided serialized
      * history.
@@ -107,6 +98,12 @@
           if (history.length == sessionHistoryObject.urls.length) {
             history.go(currentItemOffset);
             window.clearInterval(goWhenReady);
+
+            // Queue a reload to redirect to the target URL after history.go
+            // is processed.
+            setTimeout(() => {
+              location.reload();
+            });
            }
         }, 10);
       } catch (e) {

ios/web/web_state/web_state_observer_inttest.mm

@@ -2559,15 +2559,6 @@ TEST_P(WebStateObserverTest, RestoreSessionOnline) {
                                              /*for_main_frame=*/true))
       .WillOnce(Return(true));
 
-  // decide policy for restore_session.html?targetUrl=url0 again due to reload
-  // in onpopstate().
-  EXPECT_CALL(*decider_,
-              ShouldAllowRequest(URLMatch(CreateRedirectUrl(url0)), _))
-      .WillOnce(Return(true));
-  EXPECT_CALL(*decider_, ShouldAllowResponse(URLMatch(CreateRedirectUrl(url0)),
-                                             /*for_main_frame=*/true))
-      .WillOnce(Return(true));
-
   // Client-side redirect to |url0|.
   EXPECT_CALL(*decider_, ShouldAllowRequest(URLMatch(url0), _))
       .WillOnce(Return(true));