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

chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm

Index: chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm
diff --git a/chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm b/chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm
index 5eaf26d1d1b176bfc5e37e8b70eaa7189c5bb33f..e7de1ed417159445864f78ff76db1330d1841c7e 100644
--- a/chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm
+++ b/chrome/browser/ui/views/frame/browser_non_client_frame_view_mac.mm
@@ -69,7 +69,15 @@ gfx::Rect BrowserNonClientFrameViewMac::GetWindowBoundsForClientBounds(
 }
 
 int BrowserNonClientFrameViewMac::NonClientHitTest(const gfx::Point& point) {
-  return frame()->client_view()->NonClientHitTest(point);
+  int component = frame()->client_view()->NonClientHitTest(point);
+
+  // BrowserView::NonClientHitTest will return HTNOWHERE for points that hit
+  // the native title bar. On Mac, we need to explicitly return HTCAPTION for
+  // those points.
+  if (component == HTNOWHERE && bounds().Contains(point))
+    return HTCAPTION;
+
+  return component;
 }
 
 void BrowserNonClientFrameViewMac::GetWindowMask(const gfx::Size& size,