Views: Turn on InkDropMasks for Windows.

It seems to "just work".

Tested on:
 - Windows 10
 - Windows 10 with --disable-gpu
 - Windows 7
 - Windows 7 Classic mode (Aero disabled)

Bug: 713359
Change-Id: I04466aab7e978ad51e5e579488e29789cda9ab72
Reviewed-on: https://chromium-review.googlesource.com/961552
Commit-Queue: Tommy Li <tommycli@chromium.org>
Reviewed-by: Mohsen Izadi <mohsen@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543785}

ui/views/animation/ink_drop_host_view.cc

@@ -298,12 +298,9 @@ InkDrop* InkDropHostView::GetInkDrop() {
 }
 
 void InkDropHostView::InstallInkDropMask(ui::Layer* ink_drop_layer) {
-// Layer masks don't work on Windows. See crbug.com/713359
-#if !defined(OS_WIN)
   ink_drop_mask_ = CreateInkDropMask();
   if (ink_drop_mask_)
     ink_drop_layer->SetMaskLayer(ink_drop_mask_->layer());
-#endif
 }
 
 void InkDropHostView::ResetInkDropMask() {

ui/views/controls/native/native_view_host_aura.cc

@@ -143,17 +143,12 @@ void NativeViewHostAura::RemovedFromWidget() {
 }
 
 bool NativeViewHostAura::SetCornerRadius(int corner_radius) {
-#if defined(OS_WIN)
-  // Layer masks don't work on Windows. See crbug.com/713359
-  return false;
-#else
   mask_ = views::Painter::CreatePaintedLayer(
       views::Painter::CreateSolidRoundRectPainter(SK_ColorBLACK,
                                                   corner_radius));
   mask_->layer()->SetFillsBoundsOpaquely(false);
   InstallMask();
   return true;
-#endif
 }
 
 void NativeViewHostAura::InstallClip(int x, int y, int w, int h) {