Assert ViewsDelegate::HandleAccessibilityEvent requires non-null view

The only callers pass |this| for the view argument, so CHECK that it
isn't null and remove some dead code.

This simplifies an upcoming refactor in AXRemoteHost for mash.

TBR=msw@chromium.org

Bug: 888147
Test: existing unit tests
Change-Id: I93c9bb9ea5a9e55cbca5f51340625ffe60fe64d8
Reviewed-on: https://chromium-review.googlesource.com/c/1273991Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599272}

chrome/browser/ui/aura/accessibility/automation_manager_aura.cc

@@ -71,13 +71,10 @@ void AutomationManagerAura::Disable() {
 
 void AutomationManagerAura::HandleEvent(views::View* view,
                                         ax::mojom::Event event_type) {
-  if (!enabled_)
-    return;
+  CHECK(view);
 
-  if (!view) {
-    SendEvent(current_tree_->GetRoot(), event_type);
+  if (!enabled_)
     return;
-  }
 
   views::AXAuraObjWrapper* obj =
       views::AXAuraObjCache::GetInstance()->GetOrCreate(view);

ui/views/mus/ax_remote_host.cc

@@ -99,13 +99,10 @@ void AXRemoteHost::StopMonitoringWidget() {
 }
 
 void AXRemoteHost::HandleEvent(View* view, ax::mojom::Event event_type) {
-  if (!enabled_)
-    return;
+  CHECK(view);
 
-  if (!view) {
-    SendEvent(tree_source_->GetRoot(), event_type);
+  if (!enabled_)
     return;
-  }
 
   // Can return null for views without a widget.
   AXAuraObjWrapper* aura_obj = AXAuraObjCache::GetInstance()->GetOrCreate(view);

ui/views/views_delegate.h

@@ -126,6 +126,7 @@ class VIEWS_EXPORT ViewsDelegate {
                                        gfx::Rect* bounds,
                                        ui::WindowShowState* show_state) const;
 
+  // Handles an event on a |view|. The |view| must not be null.
   virtual void NotifyAccessibilityEvent(View* view,
                                         ax::mojom::Event event_type);