[ios/web] Don't delay clear browsing data for slimnav restoration.

Since crrev.com/c/1540371 it's been safe to trigger a clear
browsing data restore during a slimnav restore.  This is because we
DetachFromWebView during clear browsing data, and reset the
|is_restore_session_in_progress| flag.

DetachFromWebView already supports extracting restore urls from history,
so there shouldn't be any data loss.

Additionally, the delay implementation is wrong, since it's valid for a
webstate to be suspended in the tab grid  while in a slimnav restore state.
In fact, on a restart, most tabs are in that state.  So triggering clear
browsing data when that suspended tab is the 'active' tab, will hang forever.

Bug: 961726
TEST=
1.) Open a few tabs and create some navigation history for each (at least 10 navigation items)
2.) Quit the app
3.) Launch the app and quickly clear browsing data

Change-Id: Ic0a67523f5a0e2a63f31061735c12a2a27abb09f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1807025Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697361}

ios/chrome/app/main_controller.mm

@@ -2169,7 +2169,6 @@ enum class EnterTabSwitcherSnapshotResult {
     disableWebUsageDuringRemoval = NO;
   }
 
-  ProceduralBlock removeBrowsingDataBlock = ^{
   if (disableWebUsageDuringRemoval) {
     // Disables browsing and purges web views.
     // Must be called only on the main thread.
@@ -2183,47 +2182,28 @@ enum class EnterTabSwitcherSnapshotResult {
   }
 
   BrowsingDataRemoverFactory::GetForBrowserState(browserState)
-        ->Remove(timePeriod, removeMask, base::BindOnce(^{
+      ->Remove(
+          timePeriod, removeMask, base::BindOnce(^{
             // Activates browsing and enables web views.
             // Must be called only on the main thread.
             DCHECK([NSThread isMainThread]);
             if (showActivityIndicator) {
               // User interaction still needs to be disabled as a way to
               // force reload all the web states and to reset NTPs.
-                     self.interfaceProvider.mainInterface
-                         .userInteractionEnabled = NO;
-                     self.interfaceProvider.incognitoInterface
-                         .userInteractionEnabled = NO;
+              self.interfaceProvider.mainInterface.userInteractionEnabled = NO;
+              self.interfaceProvider.incognitoInterface.userInteractionEnabled =
+                  NO;
 
               [self.mainBVC.dispatcher showActivityOverlay:NO];
             }
-                   self.interfaceProvider.mainInterface.userInteractionEnabled =
+            self.interfaceProvider.mainInterface.userInteractionEnabled = YES;
+            self.interfaceProvider.incognitoInterface.userInteractionEnabled =
                 YES;
-                   self.interfaceProvider.incognitoInterface
-                       .userInteractionEnabled = YES;
             [self.currentBVC setPrimary:YES];
 
             if (completionBlock)
               completionBlock();
           }));
-  };
-
-  // Removing browsing data triggers session restore in navigation manager. If
-  // there is an in-progress session restore, wait for it to finish before
-  // attempting to clear browsing data again.
-  web::WebState* webState =
-      self.currentBVC.tabModel
-          ? self.currentBVC.tabModel.webStateList->GetActiveWebState()
-          : nullptr;
-  if (webState && webState->GetNavigationManager()) {
-    webState->GetNavigationManager()->AddRestoreCompletionCallback(
-        base::BindOnce(^{
-          removeBrowsingDataBlock();
-        }));
-    return;
-  }
-
-  removeBrowsingDataBlock();
 }
 
 #pragma mark - Navigation Controllers