Always set NSTexturedBackgroundWindowMask on app windows.

chrome/browser/ui/cocoa/apps/native_app_window_cocoa.mm

 // Copyright 2013 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 "chrome/browser/ui/cocoa/apps/native_app_window_cocoa.h"
 
 #include "apps/app_shim/extension_app_shim_handler_mac.h"
 #include "base/command_line.h"
 #include "base/mac/mac_util.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 205 matching lines @@
 @end
 
 // TODO(jamescook): Should these be AppNSWindow to match apps::AppWindow?
 // http://crbug.com/344082
 @interface ShellNSWindow : ChromeEventProcessingWindow
 @end
 @implementation ShellNSWindow
 @end
 
 @interface ShellCustomFrameNSWindow : ShellNSWindow
-
 - (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view;
-
 @end
 
 @implementation ShellCustomFrameNSWindow
 
 - (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view {
   [[NSBezierPath bezierPathWithRect:rect] addClip];
   [[NSColor clearColor] set];
   NSRectFill(rect);
 
   // Set up our clip.
   CGFloat cornerRadius = 4.0;
   if ([view respondsToSelector:@selector(roundedCornerRadius)])
     cornerRadius = [view roundedCornerRadius];
   [[NSBezierPath bezierPathWithRoundedRect:[view bounds]
                                    xRadius:cornerRadius
                                    yRadius:cornerRadius] addClip];
   [[NSColor whiteColor] set];
   NSRectFill(rect);
 }
 
 @end
 
-@interface ShellFramelessNSWindow : ShellCustomFrameNSWindow
-
+@interface ShellFramelessNSWindow : ShellNSWindow
+- (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view;

[tapted, 2014/05/29 03:35:28]

I'd move this up into the ShellNSWindow interface (and move empty implementation
into ShellNSWindow implementation). Then ShellCustomFrameNSWindow overrides it.
Feels more natural than just happening to have the same method implemented on
both child classes :)

[jackhou1, 2014/05/29 04:09:40]

ShellNSWindow is used to draw native frames, so it needs to call the default
implementation.

 @end
 
 @implementation ShellFramelessNSWindow
 
+- (void)drawCustomFrameRect:(NSRect)rect forView:(NSView*)view {}
+
 + (NSRect)frameRectForContentRect:(NSRect)contentRect
                         styleMask:(NSUInteger)mask {
   return contentRect;
 }
 
 + (NSRect)contentRectForFrameRect:(NSRect)frameRect
                         styleMask:(NSUInteger)mask {
   return frameRect;
 }
 
@@ skipping 99 matching lines @@
 
   extension_keybinding_registry_.reset(new ExtensionKeybindingRegistryCocoa(
       Profile::FromBrowserContext(app_window_->browser_context()),
       window,
       extensions::ExtensionKeybindingRegistry::PLATFORM_APPS_ONLY,
       NULL));
 }
 
 NSUInteger NativeAppWindowCocoa::GetWindowStyleMask() const {
   NSUInteger style_mask = NSTitledWindowMask | NSClosableWindowMask |
-                          NSMiniaturizableWindowMask;
+                          NSMiniaturizableWindowMask |
+                          NSTexturedBackgroundWindowMask;

[tapted, 2014/05/29 03:35:28]

The documentation suggests that adding this has a side-effect of "always"
drawing the window with rounded corners.. but I guess that's fine since I don't
think there's a way for a packaged app to have square corners currently if they
wanted to..

[jackhou1, 2014/05/29 04:09:40]

Yeah, and I think this only applies for native frames. I.e. we can still make
ShellCustomFrameNSWindow draw whatever we want. That said,
ShellFramelessNSWindow seems to have rounded bottom corners regardless of
whether this is set.

   if (shows_resize_controls_)
     style_mask |= NSResizableWindowMask;
-  if (!has_frame_ ||
-      !CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kAppsUseNativeFrame)) {
-    style_mask |= NSTexturedBackgroundWindowMask;
-  }
   return style_mask;
 }
 
 void NativeAppWindowCocoa::InstallView() {
   NSView* view = WebContents()->GetNativeView();
   if (has_frame_) {
     [view setFrame:[[window() contentView] bounds]];
     [[window() contentView] addSubview:view];
     if (!shows_fullscreen_controls_)
       [[window() standardWindowButton:NSWindowZoomButton] setEnabled:NO];
@@ skipping 558 matching lines @@
 }
 
 void NativeAppWindowCocoa::UpdateRestoredBounds() {
   if (IsRestored(*this))
     restored_bounds_ = [window() frame];
 }
 
 void NativeAppWindowCocoa::HideWithoutMarkingHidden() {
   [window() orderOut:window_controller_];
 }