Add debugging for ApplyViewportChanges crash.

Seems that WebViewImpl may be null, but that doesn't make much sense.
Add a few checks to see if they fire.

BUG=1160652

Change-Id: I5979a5ad62d91f9b8868d5ce72f29b47297e2c56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611126Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840310}

third_party/blink/renderer/core/frame/web_frame_widget_impl.cc

@@ -2053,7 +2053,11 @@ void WebFrameWidgetImpl::ApplyViewportChanges(
   // Viewport changes only change the main frame.
   if (!ForMainFrame())
     return;
-  View()->ApplyViewportChanges(args);
+  WebViewImpl* web_view = View();
+  // TODO(https://crbug.com/1160652): Figure out if View is null.
+  CHECK(widget_base_);
+  CHECK(web_view);
+  web_view->ApplyViewportChanges(args);
 }
 
 void WebFrameWidgetImpl::RecordManipulationTypeCounts(