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

ui/views/cocoa/bridged_native_widget.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.
 
 #import "ui/views/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 664 matching lines @@
 }
 
 void BridgedNativeWidget::OnSizeChanged() {
   gfx::Size new_size = GetClientAreaSize();
   native_widget_mac_->GetWidget()->OnNativeWidgetSizeChanged(new_size);
   if (layer()) {
     UpdateLayerProperties();
     if ([window_ inLiveResize])
       MaybeWaitForFrame(new_size);
   }
+
+  // 10.9 is unable to generate a window shadow from the composited CALayer, so
+  // use Quartz.
+  // We don't update the window mask during a live resize, instead it is done
+  // after the resize is completed in viewDidEndLiveResize: in
+  // BridgedContentView.
+  if (base::mac::IsOSMavericksOrEarlier() && ![window_ inLiveResize])
+    [bridged_view_ updateWindowMask];
 }
 
 void BridgedNativeWidget::OnVisibilityChanged() {
   OnVisibilityChangedTo([window_ isVisible]);
 }
 
 void BridgedNativeWidget::OnVisibilityChangedTo(bool new_visibility) {
   if (window_visible_ == new_visibility)
     return;
 
@@ skipping 163 matching lines @@
   layer()->SetFillsBoundsOpaquely(!translucent);
 
   // Use the regular window background for window modal sheets. The layer() will
   // still paint over most of it, but the native -[NSApp beginSheet:] animation
   // blocks the UI thread, so there's no way to invalidate the shadow to match
   // the composited layer. This assumes the native window shape is a good match
   // for the composited NonClientFrameView, which should be the case since the
   // native shape is what's most appropriate for displaying sheets on Mac.
   if (translucent && !native_widget_mac_->IsWindowModalSheet()) {
     [window_ setOpaque:NO];
-    [window_ setBackgroundColor:[NSColor clearColor]];
+    // For Mac OS versions earlier than Yosemite, the Window server isn't able
+    // to generate a window shadow from the composited CALayer. To get around
+    // this, set an opaque background on the window and clip the window boundary
+    // in drawRect method of BridgedContentView. See crbug.com/543671.
+    if (base::mac::IsOSYosemiteOrLater())
+      [window_ setBackgroundColor:[NSColor clearColor]];
+    else
+      [window_ setBackgroundColor:[NSColor whiteColor]];

[tapted, 2016/02/11 01:47:23]

I just realised.. this `else` might not be needed. (i.e. can just use the
default window background?)

[karandeepb, 2016/02/11 04:16:04]

Done.

   }
 
   UpdateLayerProperties();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // BridgedNativeWidget, internal::InputMethodDelegate:
 
 ui::EventDispatchDetails BridgedNativeWidget::DispatchKeyEventPostIME(
     ui::KeyEvent* key) {
@@ skipping 346 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views