Fix label mask for holding space item chip views in RTL.

Previously the label mask canvas was not flipped for RTL so the wrong
end of the label was being faded out.

Bug: 1166270
Change-Id: Ib3afc1c6dd676788eb58ed16eacb18cb65141fd9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627979Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#843169}

ash/system/holding_space/holding_space_item_chip_view.cc

@@ -13,6 +13,7 @@
 #include "ash/system/holding_space/holding_space_item_view.h"
 #include "ash/system/holding_space/holding_space_util.h"
 #include "ui/compositor/paint_recorder.h"
+#include "ui/gfx/scoped_canvas.h"
 #include "ui/gfx/skia_paint_util.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
@@ -96,6 +97,10 @@ class HoldingSpaceItemChipView::LabelMaskLayerOwner : public ui::LayerDelegate {
         static_cast<float>(paint_recording_size.height()) / size.height(),
         /*cache*/ nullptr);
 
+    // Flip canvas for RTL.
+    gfx::ScopedCanvas canvas(recorder.canvas());
+    canvas.FlipIfRTL(size.width());
+
     cc::PaintFlags flags;
     flags.setAntiAlias(false);