[iOS] Remove coordinator checks from OverlayPresentationContextImpl

After crrev.com/c/1787562, OverlayPresenter will only present upon the
presentation context when its presentation capabilities are sufficient
to support the current request.  Before that CL, OverlayPresenterImpl
simply used the presence of a non-null presentation context  as a signal
for when presentation was possible, and would call ShowOverlayUI() on
that context even if it was not yet provided with a coordinator capable
of showing that request's UI.  OverlayPresentationContextImpl simulated
the presentation flow for requests sent by OverlayPresenter when the
backing coordinator was null.  After crrev.com/c/1787562, these
condition blocks can be replaced with DCHECKs since the overlay UI
presentating/cancelling/hiding functionality will not be called for
unsupported requests.

Bug: none
Change-Id: Ia3bed1ffbf771f1b0deb0d17a81662111fec79c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2056206
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741642}

ios/chrome/browser/overlays/public/overlay_presentation_context.h

@@ -53,6 +53,7 @@ class OverlayPresentationContext {
   // |presentation_callback| must be called when the UI is finished being
   // presented. |dismissal_callback| must be stored and called whenever the UI
   // is finished being dismissed for user interaction, hiding, or cancellation.
+  // Must only be called when CanShowUIForRequest() returns true for |request|.
   virtual void ShowOverlayUI(OverlayPresenter* presenter,
                              OverlayRequest* request,
                              OverlayPresentationCallback presentation_callback,
@@ -63,6 +64,7 @@ class OverlayPresentationContext {
   // serialized so that the state can be restored if shown again.  When hiding
   // an overlay, the presented UI must be dismissed, and the overlay's
   // dismissal callback must must be executed upon the dismissal's completion.
+  // Must only be called when |request| is displayed within the context.
   virtual void HideOverlayUI(OverlayPresenter* presenter,
                              OverlayRequest* request) = 0;
 

ios/chrome/browser/ui/overlays/overlay_presentation_context_impl.mm

@@ -129,19 +129,14 @@ void OverlayPresentationContextImpl::HideOverlayUI(OverlayPresenter* presenter,
                                                    OverlayRequest* request) {
   DCHECK_EQ(presenter_, presenter);
   DCHECK_EQ(request_, request);
+  DCHECK(CanShowUIForRequest(request));
 
   OverlayRequestUIState* state = GetRequestUIState(request_);
   DCHECK(state->has_callback());
 
-  if (coordinator_) {
-    // If the request's UI is presented by the coordinator, dismiss it.  The
-    // presented request will be reset when the dismissal animation finishes.
-    DismissPresentedUI(OverlayDismissalReason::kHiding);
-  } else {
-    // Simulate dismissal if there is no container coordinator.
-    state->set_dismissal_reason(OverlayDismissalReason::kHiding);
-    OverlayUIWasDismissed();
-  }
+  // Hide the overlay UI.  The presented request will be reset when the
+  // dismissal animation finishes.
+  DismissPresentedUI(OverlayDismissalReason::kHiding);
 }
 
 void OverlayPresentationContextImpl::CancelOverlayUI(
@@ -163,15 +158,7 @@ void OverlayPresentationContextImpl::CancelOverlayUI(
     return;
   }
 
-  // If the current request is being cancelled (e.g. for WebState closures) when
-  // there is no coordinator, simulate a dismissal.
-  if (!coordinator_) {
-    DCHECK_EQ(request_, request);
-    state->set_dismissal_reason(OverlayDismissalReason::kCancellation);
-    state->OverlayUIWasDismissed();
-    return;
-  }
-
+  DCHECK(CanShowUIForRequest(request));
   DismissPresentedUI(OverlayDismissalReason::kCancellation);
 }
 
@@ -199,10 +186,11 @@ void OverlayPresentationContextImpl::SetRequest(OverlayRequest* request) {
 
   request_ = request;
 
-  // The UI state should be created before resetting the presented request.
-  DCHECK(!request_ || GetRequestUIState(request_));
-
-  ShowUIForPresentedRequest();
+  if (request_) {
+    // The UI state should be created before resetting the presented request.
+    DCHECK(GetRequestUIState(request_));
+    ShowUIForPresentedRequest();
+  }
 }
 
 OverlayRequestUIState* OverlayPresentationContextImpl::GetRequestUIState(
@@ -247,11 +235,11 @@ void OverlayPresentationContextImpl::UpdateForCoordinator(
 #pragma mark Presentation and Dismissal helpers
 
 void OverlayPresentationContextImpl::ShowUIForPresentedRequest() {
-  OverlayRequestUIState* state = GetRequestUIState(request_);
-  if (!state || !coordinator_)
-    return;
+  DCHECK(request_);
+  DCHECK(CanShowUIForRequest(request_));
 
   // Create the coordinator if necessary.
+  OverlayRequestUIState* state = GetRequestUIState(request_);
   UIViewController* container_view_controller = coordinator_.viewController;
   OverlayRequestCoordinator* overlay_coordinator = state->coordinator();
   if (!overlay_coordinator ||
@@ -280,7 +268,6 @@ void OverlayPresentationContextImpl::DismissPresentedUI(
     OverlayDismissalReason reason) {
   OverlayRequestUIState* state = GetRequestUIState(request_);
   DCHECK(state);
-  DCHECK(coordinator_);
   DCHECK(state->coordinator());
 
   state->set_dismissal_reason(reason);