[iOS Clean] Removed old overlay implementation.

ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.h"
 
 #include "base/logging.h"
 #import "ios/chrome/browser/web_state_list/web_state_list.h"
 #import "ios/clean/chrome/browser/ui/overlay_service/browser_coordinator+overlay_support.h"
 #import "ios/clean/chrome/browser/ui/overlay_service/internal/browser_overlay_queue.h"
@@ skipping 44 matching lines @@
   DCHECK(overlay_coordinator);
   DCHECK(IsBrowserShowingOverlay(browser));
   OverlayScheduler::FromBrowser(browser)->ReplaceVisibleOverlay(
       overlay_coordinator);
 }
 
 void OverlayServiceImpl::ShowOverlayForWebState(
     BrowserCoordinator* overlay_coordinator,
     web::WebState* web_state) {
   DCHECK(overlay_coordinator.supportsOverlaying);
-  WebStateOverlayQueue::FromWebState(web_state)->AddWebStateOverlay(
-      overlay_coordinator);
+  WebStateOverlayQueue* queue = WebStateOverlayQueue::FromWebState(web_state);
+  if (queue)
+    queue->AddWebStateOverlay(overlay_coordinator);
 }
 
 void OverlayServiceImpl::SetWebStateParentCoordinator(
     BrowserCoordinator* parent_coordinator,
     web::WebState* web_state) {
-  WebStateOverlayQueue::FromWebState(web_state)->SetWebStateParentCoordinator(
-      parent_coordinator);
+  WebStateOverlayQueue* queue = WebStateOverlayQueue::FromWebState(web_state);
+  if (queue)
+    queue->SetWebStateParentCoordinator(parent_coordinator);
 }
 
 void OverlayServiceImpl::ShowOverlayForBrowser(
     BrowserCoordinator* overlay_coordinator,
     BrowserCoordinator* parent_coordiantor,
     Browser* browser) {
   DCHECK(overlay_coordinator.supportsOverlaying);
-  BrowserOverlayQueue::FromBrowser(browser)->AddBrowserOverlay(
-      overlay_coordinator, parent_coordiantor);
+  BrowserOverlayQueue* queue = BrowserOverlayQueue::FromBrowser(browser);
+  if (queue)
+    queue->AddBrowserOverlay(overlay_coordinator, parent_coordiantor);
 }
 
 void OverlayServiceImpl::CancelOverlays() {
   for (int i = 0; i < browser_list_->count(); ++i) {
     OverlayScheduler::FromBrowser(browser_list_->GetBrowserAtIndex(i))
         ->CancelOverlays();
   }
 }
 
 void OverlayServiceImpl::CancelOverlayForWebState(web::WebState* web_state) {
-  WebStateOverlayQueue::FromWebState(web_state)->CancelOverlays();
+  OverlayQueue* queue = WebStateOverlayQueue::FromWebState(web_state);
+  if (queue)
+    queue->CancelOverlays();
 }
 
 void OverlayServiceImpl::StartSchedulerForBrowser(Browser* browser) {
-  OverlayScheduler::CreateForBrowser(browser);
+  OverlayScheduler* scheduler = OverlayScheduler::FromBrowser(browser);
+  if (scheduler) {
+    scheduler->StartObservingBrowser();
+  } else {
+    OverlayScheduler::CreateForBrowser(browser);
+  }
 }
 
 void OverlayServiceImpl::StopSchedulerForBrowser(Browser* browser) {
   OverlayScheduler::FromBrowser(browser)->StopObservingBrowser();
 }