Add a 1px border stroke to the shelf button active app indicator.

ash/common/shelf/shelf_button.cc

Index: ash/common/shelf/shelf_button.cc
diff --git a/ash/common/shelf/shelf_button.cc b/ash/common/shelf/shelf_button.cc
index b39fa9c2f785d3bd2c4c23ae58b1dd20de0d3ccc..5df12a6ec062139f3f8eddb91694e534ebf78624 100644
--- a/ash/common/shelf/shelf_button.cc
+++ b/ash/common/shelf/shelf_button.cc
@@ -146,11 +146,23 @@ class ShelfButton::AppStatusIndicatorView
 
     DCHECK_EQ(width(), height());
     DCHECK_EQ(kIndicatorRadiusDip, width() / 2);
+    const float dsf = canvas->UndoDeviceScaleFactor();

[Daniel Erat, 2017/03/03 23:15:52]

i don't know much about device scale factors, but should you be wrapping all of
this in Save/Restore calls to ensure that the original scale is restored? is it
just safe to do here because this is at the end of the method?

[Evan Stade, 2017/03/04 01:02:22]

the scopedcanvas above takes care of that. Technically I think it isn't even
necessary because a new canvas is created for every View::OnPaint, but it's hard
to keep track of when you need it and when not, so I just always add it.

[Daniel Erat, 2017/03/04 01:17:05]

ah, sorry. i missed both the fact that a ScopedCanvas class exists and that you
were already using it here. carry on.

+    const int kStrokeWidthPx = 1;
+    gfx::PointF center = gfx::RectF(GetLocalBounds()).CenterPoint();
+    center.Scale(dsf);
+
+    // Fill the center.
     cc::PaintFlags flags;
     flags.setColor(kIndicatorColor);
     flags.setFlags(cc::PaintFlags::kAntiAlias_Flag);
-    canvas->DrawCircle(gfx::Point(width() / 2, height() / 2),
-                       kIndicatorRadiusDip, flags);
+    canvas->DrawCircle(center, dsf * kIndicatorRadiusDip - kStrokeWidthPx,
+                       flags);
+
+    // Stroke the border.
+    flags.setColor(SkColorSetA(SK_ColorBLACK, 0x29));
+    flags.setStyle(SkPaint::kStroke_Style);
+    canvas->DrawCircle(
+        center, dsf * kIndicatorRadiusDip - kStrokeWidthPx / 2.0f, flags);
   }
 
   // ShelfButtonAnimation::Observer