Cancel drag operation when the tab RenderWidgetHostView does not exist (Mac)

content/browser/web_contents/web_drag_dest_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "content/browser/web_contents/web_drag_dest_mac.h"
 
 #import <Carbon/Carbon.h>
 
 #include "base/strings/sys_string_conversions.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
@@ skipping 116 matching lines @@
   // Save off the RVH so we can tell if it changes during a drag. If it does,
   // we need to send a new enter message in draggingUpdated:.
   currentRVH_ = webContents_->GetRenderViewHost();
 
   // Create the appropriate mouse locations for WebCore. The draggingLocation
   // is in window coordinates. Both need to be flipped.
   NSPoint windowPoint = [info draggingLocation];
   NSPoint viewPoint = [self flipWindowPointToView:windowPoint view:view];
   NSPoint screenPoint = [self flipWindowPointToScreen:windowPoint view:view];
   gfx::Point transformedPt;
+  if (!webContents_->GetRenderWidgetHostView()) {
+    // TODO(ekaramad, paulmeyer): Find a better way than toggling |canceled_|.
+    // This could happen when the renderer process for the top-level RWH crashes
+    // (see https://crbug.com/670645).
+    canceled_ = true;
+    return NSDragOperationNone;
+  }
   currentRWHForDrag_ =
       [self GetRenderWidgetHostAtPoint:viewPoint transformedPt:&transformedPt]
           ->GetWeakPtr();
 
   // Fill out a DropData from pasteboard.
   std::unique_ptr<DropData> dropData;
   dropData.reset(new DropData());
   [self populateDropData:dropData.get()
              fromPasteboard:[info draggingPasteboard]];
   // TODO(paulmeyer): Data may be pulled from the pasteboard multiple times per
@@ skipping 47 matching lines @@
   if (delegate_)
     delegate_->OnDragLeave();
 
   if (currentRWHForDrag_) {
     currentRWHForDrag_->DragTargetDragLeave();
     currentRWHForDrag_.reset();
   }
   dropData_.reset();
 }
 
-- (NSDragOperation)draggingUpdated:(id<NSDraggingInfo>)info
-                              view:(NSView*)view {
+- (NSDragOperation)draggingUpdated:(id<NSDraggingInfo>)info view:(NSView*)view {
+  if (canceled_) {
+    // TODO(ekaramad,paulmeyer): We probably shouldn't be checking for
+    // |canceled_| twice in this method.
+    return NSDragOperationNone;
+  }
+
   // Create the appropriate mouse locations for WebCore. The draggingLocation
   // is in window coordinates. Both need to be flipped.
   NSPoint windowPoint = [info draggingLocation];
   NSPoint viewPoint = [self flipWindowPointToView:windowPoint view:view];
   NSPoint screenPoint = [self flipWindowPointToScreen:windowPoint view:view];
   gfx::Point transformedPt;
   content::RenderWidgetHostImpl* targetRWH =
       [self GetRenderWidgetHostAtPoint:viewPoint transformedPt:&transformedPt];
 
   // TODO(paulmeyer): The dragging delegates may now by invoked multiple times
@@ skipping 138 matching lines @@
   // Get custom MIME data.
   if ([types containsObject:ui::kWebCustomDataPboardType]) {
     NSData* customData = [pboard dataForType:ui::kWebCustomDataPboardType];
     ui::ReadCustomDataIntoMap([customData bytes],
                               [customData length],
                               &data->custom_data);
   }
 }
 
 @end