[MacViews] Implement colored window frames.

ui/gfx/mac/nswindow_frame_controls.h

 // Copyright 2015 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.
 
 #ifndef UI_GFX_MAC_NSWINDOW_FRAME_CONTROLS_H_
 #define UI_GFX_MAC_NSWINDOW_FRAME_CONTROLS_H_
 
+#import <Cocoa/Cocoa.h>
+
+#include "base/mac/scoped_nsobject.h"
+#include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/gfx_export.h"
 
-@class NSWindow;
+// A view that paints a solid color. Used to change the title bar background.
+GFX_EXPORT @interface TitlebarBackgroundView : NSView {
+ @private
+  base::scoped_nsobject<NSColor> color_;
+  base::scoped_nsobject<NSColor> inactiveColor_;
+}
+- (void)setColor:(NSColor*)color inactiveColor:(NSColor*)inactiveColor;
+@end
 
-namespace gfx {
-
+    namespace gfx {
 class Size;
 
 // Set whether the window can be fullscreened.
 GFX_EXPORT void SetNSWindowCanFullscreen(NSWindow* window,
                                          bool allow_fullscreen);
 
 // Sets the min/max size of the window as well as showing/hiding resize,
 // maximize, and fullscreen controls.
 // Sizes refer to the content size (inner bounds).
 GFX_EXPORT void ApplyNSWindowSizeConstraints(NSWindow* window,
                                              const gfx::Size& min_size,
                                              const gfx::Size& max_size,
                                              bool can_resize,
                                              bool can_fullscreen);
 
+// Adds a TitlebarBackgroundView to the [[window contentView] superView].
+GFX_EXPORT void AddColoredTitlebarToNSWindow(

[jackhou1, 2015/04/24 07:05:03]

Should we merge TitlebarBackgroundView and TabStripBackgroundView?

[tapted, 2015/05/06 02:58:29]

I'd lean towards "nah" - probably not enough in common - just an NSBezierPath.

The common bit might be
`gfx::ClipCurrentDrawingContextToRoundedWindow(NSWindow*)`, but there's too many
temporaries needed later

+    NSWindow * window, SkColor active_color, SkColor inactive_color);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_MAC_NSWINDOW_FRAME_CONTROLS_H_