Fix Views overlay scrollbar border stroke.

ui/views/controls/scrollbar/overlay_scroll_bar.cc

Index: ui/views/controls/scrollbar/overlay_scroll_bar.cc
diff --git a/ui/views/controls/scrollbar/overlay_scroll_bar.cc b/ui/views/controls/scrollbar/overlay_scroll_bar.cc
index 83d7a58ba6dca52f64edf15a47581667889510dd..ae0c2619822cd7ddd2940618bf6206e0c55c165f 100644
--- a/ui/views/controls/scrollbar/overlay_scroll_bar.cc
+++ b/ui/views/controls/scrollbar/overlay_scroll_bar.cc
@@ -67,6 +67,7 @@ void OverlayScrollBar::Thumb::OnPaint(gfx::Canvas* canvas) {
   stroke_flags.setStyle(cc::PaintFlags::kStroke_Style);
   stroke_flags.setColor(SK_ColorWHITE);
   stroke_flags.setStrokeWidth(kThumbStroke);
+  stroke_flags.setStrokeCap(cc::PaintFlags::kSquare_Cap);
   gfx::RectF stroke_bounds(fill_bounds);
   stroke_bounds.Inset(gfx::InsetsF(kThumbStroke / 2.f));
   // The stroke doesn't apply to the far edge of the thumb.