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

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

Index: chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc
diff --git a/chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc b/chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc
index a7af6502ee5e157670546370f86bfe63effd8fdb..5d7a6c0980a4ed647dd463a3de4e474efde2f593 100644
--- a/chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc
+++ b/chrome/browser/ui/views/autofill/card_unmask_prompt_views.cc
@@ -463,10 +463,8 @@ 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);
 }