[iOS Clean] Removed old overlay implementation.

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

Index: ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm
diff --git a/ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm b/ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm
index fec6060bf09a55b76be75a9e6983795801810aad..b1a6f7dc67955f8bc418245dc25f450e1da3dc35 100644
--- a/ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm
+++ b/ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.mm
@@ -62,15 +62,17 @@
     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(
@@ -78,8 +80,9 @@
     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() {
@@ -90,11 +93,18 @@
 }
 
 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) {