gfx: Rename canvas SaveAndUnscale to UnscaleTheDeviceScaleFactor.

ash/frame/default_header_painter.cc

Index: ash/frame/default_header_painter.cc
diff --git a/ash/frame/default_header_painter.cc b/ash/frame/default_header_painter.cc
index ab9dd1806f17940a428f9d920d350e5048d10085..60d4f495de752186af9f32ca274a3907869e2d2e 100644
--- a/ash/frame/default_header_painter.cc
+++ b/ash/frame/default_header_painter.cc
@@ -262,13 +262,13 @@ void DefaultHeaderPainter::PaintTitleBar(gfx::Canvas* canvas) {
 }
 
 void DefaultHeaderPainter::PaintHeaderContentSeparator(gfx::Canvas* canvas) {
-  const float scale = canvas->SaveAndUnscale();
+  ScopedCanvas scoped(canvas);

[Peter Kasting, 2015/10/29 23:11:10]

The variable name "scoped" doesn't really pass style-guide muster -- I think you
should use "scoped_canvas" or "canvas_scoper" here and elsewhere in this change.

[danakj, 2015/10/30 17:51:21]

Done.

+  const float scale = canvas->UnscaleTheDeviceScaleFactor();
   gfx::RectF rect(0, painted_height_ * scale - 1, view_->width() * scale, 1);
   SkPaint paint;
   paint.setColor((mode_ == MODE_ACTIVE) ?
       kHeaderContentSeparatorColor : kHeaderContentSeparatorInactiveColor);
   canvas->sk_canvas()->drawRect(gfx::RectFToSkRect(rect), paint);
-  canvas->Restore();
 }
 
 void DefaultHeaderPainter::LayoutLeftHeaderView() {