[MacViews] Enable dragging a window by its caption/draggable areas.

ui/views/cocoa/bridged_native_widget.h

Index: ui/views/cocoa/bridged_native_widget.h
diff --git a/ui/views/cocoa/bridged_native_widget.h b/ui/views/cocoa/bridged_native_widget.h
index badda952339963177b0c5ded3ec992bb78f4d53e..68f81f5edc334fe047bfad82e5cf6af277917625 100644
--- a/ui/views/cocoa/bridged_native_widget.h
+++ b/ui/views/cocoa/bridged_native_widget.h
@@ -29,6 +29,7 @@ class InputMethod;
 namespace views {
 
 class CocoaMouseCapture;
+class CocoaNonClientDrag;
 class InputMethod;
 class NativeWidgetMac;
 class View;
@@ -132,6 +133,11 @@ class VIEWS_EXPORT BridgedNativeWidget : public ui::LayerDelegate,
   // Called by the NSWindowDelegate when the window becomes or resigns key.
   void OnWindowKeyStatusChangedTo(bool is_key);
 
+  // Called when the application receives a mouse-down, but before the event
+  // is processed by NSWindows. Returning true here will cause the event to be
+  // reposted.
+  bool OnWindowWillReceiveLeftMouseDown(NSPoint location_in_window);
+
   // Called by NativeWidgetMac when the window size constraints change.
   void OnSizeConstraintsChanged();
 
@@ -228,6 +234,7 @@ class VIEWS_EXPORT BridgedNativeWidget : public ui::LayerDelegate,
   base::scoped_nsobject<BridgedContentView> bridged_view_;
   scoped_ptr<ui::InputMethod> input_method_;
   scoped_ptr<CocoaMouseCapture> mouse_capture_;
+  scoped_ptr<CocoaNonClientDrag> non_client_drag_;
   FocusManager* focus_manager_;  // Weak. Owned by our Widget.
   Widget::InitParams::Type widget_type_;
 
@@ -259,6 +266,12 @@ class VIEWS_EXPORT BridgedNativeWidget : public ui::LayerDelegate,
   // currently hidden due to having a hidden parent.
   bool wants_to_be_visible_;
 
+  // Whether the window's content view is currently draggable. Initially true

[jackhou1, 2015/05/20 05:50:36]

This should initially be false, but we'd need to add the
CocoaNonClientDragMaskView after the webcontents has been added to the content
view. Another way to do this would be to set/unset mouseDownCanMoveWindow on the
content view, which eliminates the CocoaNonClientDragMaskView. I will look into
that.

This is done in Patch Set 3.

+  // because we make it non-draggable by adding a CocoaNonClientDragMaskView
+  // to the content view. After that, this is only true while we're handling
+  // a mouse-down that should drag the window.
+  bool draggable_ = true;
+
   DISALLOW_COPY_AND_ASSIGN(BridgedNativeWidget);
 };