Bug 1152585 - Implement GetClientOffset in nsChildView to fix child offset calculation when drawInTitlebar=false r=mstange

widget/cocoa/nsChildView.h

@@ -543,6 +543,8 @@ public:
 
   bool IsPluginFocused() { return mPluginFocused; }
 
+  virtual nsIntPoint GetClientOffset() override;
+
 protected:
   virtual ~nsChildView();
 

widget/cocoa/nsChildView.mm

@@ -1485,6 +1485,17 @@ void nsChildView::ReportSizeEvent()
 
 #pragma mark -
 
+nsIntPoint nsChildView::GetClientOffset()
+{
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_RETURN;
+
+  NSPoint origin = [mView convertPoint:NSMakePoint(0, 0) toView:nil];
+  origin.y = [[mView window] frame].size.height - origin.y;
+  return CocoaPointsToDevPixels(origin);
+
+  NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(nsIntPoint(0, 0));
+}
+
 //    Return the offset between this child view and the screen.
 //    @return       -- widget origin in device-pixel coords
 LayoutDeviceIntPoint nsChildView::WidgetToScreenOffset()