Wires up immersive mode for chrome and mash

ash/mus/frame/custom_frame_view_mus.cc

+// Copyright 2016 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 "ash/mus/frame/custom_frame_view_mus.h"
+
+#include "ui/compositor/paint_cache.h"
+#include "ui/compositor/paint_recorder.h"
+#include "ui/gfx/canvas.h"
+
+namespace ash {
+namespace mus {
+
+CustomFrameViewMus::CustomFrameViewMus(
+    views::Widget* widget,
+    ImmersiveFullscreenControllerDelegate* immersive_delegate,
+    bool enable_immersive)
+    : CustomFrameViewAsh(widget, immersive_delegate, enable_immersive) {}
+
+CustomFrameViewMus::~CustomFrameViewMus() {}
+
+void CustomFrameViewMus::OnPaint(gfx::Canvas* canvas) {
+  canvas->Save();
+  CustomFrameViewAsh::OnPaint(canvas);
+  canvas->Restore();
+
+  // The client app draws the client area. Make ours totally transparent so
+  // we only see the client apps client area.

[James Cook, 2016/08/24 17:00:32]

super nit: apps -> app's

[sky, 2016/08/24 19:23:28]

Done.

+  canvas->FillRect(GetBoundsForClientView(), SK_ColorBLACK,

[James Cook, 2016/08/24 17:00:32]

Dumb question: Why is this SK_ColorBLACK? How does that end up in the client
area being transparent? (and below)

[sky, 2016/08/24 19:23:29]

Not a dumb question. This should be kClear_Mode. Fixed.

+                   SkXfermode::kSrc_Mode);
+}
+
+void CustomFrameViewMus::PaintChildren(const ui::PaintContext& context) {
+  CustomFrameViewAsh::PaintChildren(context);
+  // The client app draws the client area. Make ours totally transparent so
+  // we only see the client apps client area.
+  ui::PaintRecorder recorder(context, size(), &paint_cache_);
+  recorder.canvas()->FillRect(GetBoundsForClientView(), SK_ColorBLACK,
+                              SkXfermode::kSrc_Mode);
+}
+
+}  // namespace mus
+}  // namespace ash