blink::WebViewImpl: Use Unretained instead of WeakPtr for mojo::Remote calls.

mojo::Remote already handles cancellation, so it's not necessary to have
a redundant layer of cancellation with WeakPtr.

Change-Id: Icda83b38d04eb5ba4a914c21933524a669b617ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490441Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819492}

third_party/blink/renderer/core/exported/web_view_impl.cc

@@ -3491,16 +3491,18 @@ void WebViewImpl::UpdateTargetURL(const WebURL& url,
 }
 
 void WebViewImpl::SendUpdatedTargetURLToBrowser(const KURL& target_url) {
+  // Note: WTF::Unretained() usage below is safe, since `this` owns both
+  // `mojo::Remote` objects.
   if (GetPage()->MainFrame()->IsLocalFrame()) {
     DCHECK(local_main_frame_host_remote_);
     local_main_frame_host_remote_->UpdateTargetURL(
         target_url, WTF::Bind(&WebViewImpl::TargetURLUpdatedInBrowser,
-                              weak_ptr_factory_.GetWeakPtr()));
+                              WTF::Unretained(this)));
   } else {
     DCHECK(remote_main_frame_host_remote_);
     remote_main_frame_host_remote_->UpdateTargetURL(
         target_url, WTF::Bind(&WebViewImpl::TargetURLUpdatedInBrowser,
-                              weak_ptr_factory_.GetWeakPtr()));
+                              WTF::Unretained(this)));
   }
 }