tabstrip: Use a PaintRecorder to access the Canvas for painting.

chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc

 // 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 "chrome/browser/ui/views/autofill/card_unmask_prompt_views.h"
 
 #include "base/basictypes.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/ui/autofill/autofill_dialog_types.h"
 #include "chrome/browser/ui/autofill/card_unmask_prompt_controller.h"
@@ skipping 445 matching lines @@
 }
 
 CardUnmaskPromptViews::FadeOutView::FadeOutView()
     : fade_everything_(false), opacity_(1.0) {
 }
 CardUnmaskPromptViews::FadeOutView::~FadeOutView() {
 }
 
 void CardUnmaskPromptViews::FadeOutView::PaintChildren(
     const ui::PaintContext& context) {
-  if (opacity_ > 0.99)
-    return views::View::PaintChildren(context);
-
-  ui::CompositingRecorder recorder(context, opacity_);
+  int alpha = static_cast<int>(255 * opacity_);

[Peter Kasting, 2015/04/07 21:32:39]

Probably not very important, but it seems like this should round rather than
truncating.  (Use gfx::ToRoundedInt().)

Perhaps even better would be to simply have |opacity_| be integral instead of
floating-point.  I think this could be trivially done by using
CurrentValueBetween() with the animation on the caller side to translate the
underlying animation state into an opacity.

[danakj, 2015/04/07 21:36:25]

Sure, I was just maintaining what this did before, am happy to make it better.
Can I do that in another CL though? I want to try not make changes at the same
time as refactoring.

[danakj, 2015/04/07 21:43:38]

Here's a followup: https://codereview.chromium.org/1064213002

[Peter Kasting, 2015/04/07 21:45:59]

You're welcome to do it either way, though I think the changes are so simple
that it would be less work for both of us to just do it in one CL.  But I see
you've already made a new one :)

+  ui::CompositingRecorder recorder(context, alpha);
   views::View::PaintChildren(context);
 }
 
 void CardUnmaskPromptViews::FadeOutView::OnPaint(gfx::Canvas* canvas) {
   if (!fade_everything_ || opacity_ > 0.99)
     return views::View::OnPaint(canvas);
 
   canvas->SaveLayerAlpha(0xff * opacity_);
   views::View::OnPaint(canvas);
   canvas->Restore();
 }
 
 void CardUnmaskPromptViews::FadeOutView::SetOpacity(double opacity) {
   opacity_ = opacity;
   SchedulePaint();
 }
 
 }  // namespace autofill