[ios] Don't trigger initial load when deserializing webStateList.

Don't trigger the initial load for restored WebStates since the number
of WKWebViews is unbounded and may lead to an OOM crash. Instead,
disable and re-enable WebUsageEnabler SetTriggersInitialLoad

Bug: 1018337
Change-Id: Iaccecc3c0a1e68465b31b8503eee7b6d061d4f58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879205Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709903}

ios/chrome/browser/tabs/tab_model.mm

@@ -576,11 +576,20 @@ void RecordMainFrameNavigationMetric(web::WebState* web_state) {
 
   _webStateList->PerformBatchOperation(
       base::BindOnce(^(WebStateList* web_state_list) {
+        // Don't trigger the initial load for these restored WebStates since the
+        // number of WKWebViews is unbounded and may lead to an OOM crash.
+        WebStateListWebUsageEnabler* webUsageEnabler =
+            WebStateListWebUsageEnablerFactory::GetInstance()
+                ->GetForBrowserState(_browserState);
+        const bool wasTriggersInitialLoadSet =
+            webUsageEnabler->TriggersInitialLoad();
+        webUsageEnabler->SetTriggersInitialLoad(false);
         web::WebState::CreateParams createParams(_browserState);
         DeserializeWebStateList(
             web_state_list, window,
             base::BindRepeating(&web::WebState::CreateWithStorageSession,
                                 createParams));
+        webUsageEnabler->SetTriggersInitialLoad(wasTriggersInitialLoadSet);
       }));
 
   DCHECK_GT(_webStateList->count(), oldCount);