Correct drag location

The |draggingLocation| of NSDraggingInfo is a point based on the
NSWindow coordinate and it should be converted to gfx::Point
using |contentRectForFrameRect:| instead of |frame| because the
NSWindow may have title bar.

Bug: 954019
Change-Id: I92e45aa5fb8aab07c2540cc97b5bd76e29e43a5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1573358Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654804}

ui/views/cocoa/drag_drop_client_mac.mm

@@ -125,7 +125,9 @@ void DragDropClientMac::DragExit() {
 }
 
 gfx::Point DragDropClientMac::LocationInView(NSPoint point) const {
-  return gfx::Point(point.x, NSHeight([bridge_->ns_window() frame]) - point.y);
+  NSRect content_rect = [bridge_->ns_window()
+      contentRectForFrameRect:[bridge_->ns_window() frame]];
+  return gfx::Point(point.x, NSHeight(content_rect) - point.y);
 }
 
 }  // namespace views