MacViews: Implement Tab Dragging

chrome/browser/ui/views/tabs/tab_drag_controller.cc

Index: chrome/browser/ui/views/tabs/tab_drag_controller.cc
diff --git a/chrome/browser/ui/views/tabs/tab_drag_controller.cc b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
index 2799ba073f59cc573b860c6d5872c4b71e39a606..74161394bf1ef7afbaea8f332a71b18030212c6d 100644
--- a/chrome/browser/ui/views/tabs/tab_drag_controller.cc
+++ b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
@@ -390,7 +390,10 @@ void TabDragController::Drag(const gfx::Point& point_in_screen) {
                                          &drag_bounds);
         widget->SetVisibilityChangedAnimationsEnabled(true);
       }
-      RunMoveLoop(GetWindowOffset(point_in_screen));
+      // Use the start point to initialize the move loop, otherwise the point
+      // under the cursor will be offset by the drag threshold from where the
+      // user originally clicked, which could be entirely off the window.
+      RunMoveLoop(GetWindowOffset(start_point_in_screen_));

[sky, 2016/06/07 15:57:55]

I think the right thing here is to move the window by
point_in_screen-start_point_in_screen and then start the move loop using
point_in_screen.

       return;
     }
   }