MacViews: Fix window dragging on Sierra.

ui/views/cocoa/bridged_native_widget.h

 // Copyright 2014 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.
 
 #ifndef UI_VIEWS_COCOA_BRIDGED_NATIVE_WIDGET_H_
 #define UI_VIEWS_COCOA_BRIDGED_NATIVE_WIDGET_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ skipping 49 matching lines @@
     SHOW_AND_ACTIVATE_WINDOW,  // Shows with -[NSWindow makeKeyAndOrderFront:].
     SHOW_INACTIVE,             // Shows with -[NSWindow orderWindow:..]. Orders
                                // the window above its parent if it has one.
   };
 
   // Return the size that |window| will take for the given client area |size|,
   // based on its current style mask.
   static gfx::Size GetWindowSizeForClientSize(NSWindow* window,
                                               const gfx::Size& size);
 
+  // Whether an event monitor should be used to intercept window drag events.
+  static bool ShouldUseDragEventMonitor();
+
   // Creates one side of the bridge. |parent| must not be NULL.
   explicit BridgedNativeWidget(NativeWidgetMac* parent);
   ~BridgedNativeWidget() override;
 
   // Initialize the bridge, "retains" ownership of |window|.
   void Init(base::scoped_nsobject<NSWindow> window,
             const Widget::InitParams& params);
 
   // Sets or clears the focus manager to use for tracking focused views.
   // This does NOT take ownership of |focus_manager|.
@@ skipping 64 matching lines @@
 
   // Called by the NSWindowDelegate when the system control tint changes.
   void OnSystemControlTintChanged();
 
   // Called by the NSWindowDelegate on a scale factor or color space change.
   void OnBackingPropertiesChanged();
 
   // Called by the NSWindowDelegate when the window becomes or resigns key.
   void OnWindowKeyStatusChangedTo(bool is_key);
 
-  // Called by NSWindowDelegate when the application receives a mouse-down, but
-  // before the event is processed by NSWindows. Returning true here will cause
-  // the event to be cancelled and reposted at the CGSessionEventTap level. This
-  // is used to determine whether a mouse-down should drag the window.
-  virtual bool ShouldRepostPendingLeftMouseDown(NSPoint location_in_window);
+  // Returns true if the |event| should initiate a window drag.
+  bool ShouldDragWindow(NSEvent* event);
+
+  // Called when the application receives a mouse-down, but before the event is
+  // processed by NSWindow. Returning true here will cause the event to be
+  // cancelled and reposted at the CGSessionEventTap level. This is used to
+  // determine whether a mouse-down should drag the window. Only called when
+  // ShouldUseDragEventMonitor() returns true.
+  // Virtual for testing.
+  virtual bool ShouldRepostPendingLeftMouseDown(NSEvent* event);
 
   // Called by NativeWidgetMac when the window size constraints change.
   void OnSizeConstraintsChanged();
 
   // See widget.h for documentation.
   ui::InputMethod* GetInputMethod();
 
   // The restored bounds will be derived from the current NSWindow frame unless
   // fullscreen or transitioning between fullscreen states.
   gfx::Rect GetRestoredBounds() const;
@@ skipping 151 matching lines @@
   bool initial_visibility_suppressed_ = false;
 
   AssociatedViews associated_views_;
 
   DISALLOW_COPY_AND_ASSIGN(BridgedNativeWidget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_COCOA_BRIDGED_NATIVE_WIDGET_H_