MacViews: Add native drop shadow to dialogs on OSX < 10.10.

ui/views/widget/native_widget_mac.mm

 // 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.
 
 #include "ui/views/widget/native_widget_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 484 matching lines @@
 
 void NativeWidgetMac::RunShellDrag(View* view,
                                    const ui::OSExchangeData& data,
                                    const gfx::Point& location,
                                    int operation,
                                    ui::DragDropTypes::DragEventSource source) {
   NOTIMPLEMENTED();
 }
 
 void NativeWidgetMac::SchedulePaintInRect(const gfx::Rect& rect) {
-  // TODO(tapted): This should use setNeedsDisplayInRect:, once the coordinate
-  // system of |rect| has been converted.
-  [GetNativeView() setNeedsDisplay:YES];
+  // |rect| is relative to client area of the window.

[tapted, 2016/02/10 02:28:02]

needs a rebase off the other CL (probably the order that they land doesn't
matter since it's a performance optimization)

[karandeepb, 2016/02/11 00:30:09]

Done.

+  NSWindow* window = GetNativeWindow();
+  NSRect client_rect = [window contentRectForFrameRect:[window frame]];
+  NSRect target_rect = rect.ToCGRect();
+
+  // Convert to Appkit coordinate system (origin at bottom left).
+  target_rect.origin.y =
+      NSHeight(client_rect) - target_rect.origin.y - NSHeight(target_rect);
+  [GetNativeView() setNeedsDisplayInRect:target_rect];
   if (bridge_ && bridge_->layer())
     bridge_->layer()->SchedulePaint(rect);
 }
 
 void NativeWidgetMac::SetCursor(gfx::NativeCursor cursor) {
   if (bridge_)
     bridge_->SetCursor(cursor);
 }
 
 bool NativeWidgetMac::IsMouseEventsEnabled() const {
@@ skipping 203 matching lines @@
   [[ViewsNSWindowCloseAnimator alloc] initWithWindow:window];
 }
 
 - (void)animationDidEnd:(NSAnimation*)animation {
   [window_ close];
   [animation_ setDelegate:nil];
   [self release];
 }
 
 @end