views: fix MdTextButton stroke alpha

ui/views/controls/button/md_text_button.cc

Index: ui/views/controls/button/md_text_button.cc
diff --git a/ui/views/controls/button/md_text_button.cc b/ui/views/controls/button/md_text_button.cc
index 43d7b153fc274eb01c463d866b5be109677c3bb3..b232477cc596d8b0fdd1e11c6d077438f558f193 100644
--- a/ui/views/controls/button/md_text_button.cc
+++ b/ui/views/controls/button/md_text_button.cc
@@ -264,8 +264,11 @@ void MdTextButton::UpdateColors() {
     bg_color = color_utils::GetResultingPaintColor(shade, bg_color);
   }
 
-  const SkAlpha kStrokeOpacity = 0x1A;
-  SkColor stroke_color = (is_prominent_ || color_utils::IsDark(text_color))
+  // Prominent buttons have no outside stroke at all. Fake it by using zero
+  // opacity so the code below can still use
+  // CreateRoundRectWith1PxBorderPainter().
+  const SkAlpha kStrokeOpacity = is_prominent_ ? 0x00 : 0x33;
+  SkColor stroke_color = color_utils::IsDark(text_color)
                              ? SkColorSetA(SK_ColorBLACK, kStrokeOpacity)
                              : SkColorSetA(SK_ColorWHITE, 2 * kStrokeOpacity);