EndDrag should use weak_ptr for its arg

As WebContentsViewAura::EndDrag can be arbitrary delayed waiting for the
renderer process to perform asynchronous targetting, it should use a
weak pointer for the RenderWidgetHostImpl argument.

Bug: 1034519
Change-Id: Ib8c785d3c54b448dc4b020b11112b65ced3d4261
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978000Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Navid Zolghadr <nzolghadr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744297}

content/browser/web_contents/web_contents_view_aura.cc

@@ -722,8 +722,9 @@ void WebContentsViewAura::SizeChangedCommon(const gfx::Size& size) {
     rwhv->SetSize(size);
 }
 
-void WebContentsViewAura::EndDrag(RenderWidgetHost* source_rwh,
-                                  blink::WebDragOperationsMask ops) {
+void WebContentsViewAura::EndDrag(
+    base::WeakPtr<RenderWidgetHostImpl> source_rwh_weak_ptr,
+    blink::WebDragOperationsMask ops) {
   drag_start_process_id_ = ChildProcessHost::kInvalidUniqueID;
   drag_start_view_id_ = GlobalRoutingID(ChildProcessHost::kInvalidUniqueID,
                                         MSG_ROUTING_NONE);
@@ -731,6 +732,9 @@ void WebContentsViewAura::EndDrag(RenderWidgetHost* source_rwh,
   if (!web_contents_)
     return;
 
+  // It is OK for source_rwh to be null.
+  RenderWidgetHost* source_rwh = source_rwh_weak_ptr.get();
+
   aura::Window* window = GetContentNativeView();
   gfx::PointF screen_loc =
       gfx::PointF(display::Screen::GetScreen()->GetCursorScreenPoint());
@@ -1110,11 +1114,11 @@ void WebContentsViewAura::StartDragging(
   // callback yet. So we have to make sure to delay calling EndDrag until drop
   // is done.
   if (!drag_in_progress_)
-    EndDrag(source_rwh_weak_ptr.get(), ConvertToWeb(result_op));
+    EndDrag(std::move(source_rwh_weak_ptr), ConvertToWeb(result_op));
   else
     end_drag_runner_ = base::ScopedClosureRunner(base::BindOnce(
         &WebContentsViewAura::EndDrag, weak_ptr_factory_.GetWeakPtr(),
-        source_rwh_weak_ptr.get(), ConvertToWeb(result_op)));
+        std::move(source_rwh_weak_ptr), ConvertToWeb(result_op)));
 }
 
 void WebContentsViewAura::UpdateDragCursor(blink::WebDragOperation operation) {

content/browser/web_contents/web_contents_view_aura.h

@@ -108,7 +108,8 @@ class CONTENT_EXPORT WebContentsViewAura
 
   void SizeChangedCommon(const gfx::Size& size);
 
-  void EndDrag(RenderWidgetHost* source_rwh, blink::WebDragOperationsMask ops);
+  void EndDrag(base::WeakPtr<RenderWidgetHostImpl> source_rwh_weak_ptr,
+               blink::WebDragOperationsMask ops);
 
   void InstallOverscrollControllerDelegate(RenderWidgetHostViewAura* view);