IPH: Overrides button outline color to white

Overrides button outline color to white as requested by UX. Currently
the outline is black under dark mode.

Bug: 1146259
Change-Id: I9d5a04bca5f094282b9e51d5f17aae08486b2b3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522226Reviewed-by: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Keren Zhu <kerenzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824923}

chrome/browser/ui/views/user_education/feature_promo_bubble_view.cc

@@ -56,6 +56,9 @@ constexpr gfx::Insets kBubbleButtonPadding(8, 10);
 // The text color of the button.
 constexpr SkColor kBubbleButtonTextColor = SK_ColorWHITE;
 
+// The outline color of the button.
+constexpr SkColor kBubbleButtonBorderColor = gfx::kGoogleGrey300;
+
 // The focus ring color of the button.
 constexpr SkColor kBubbleButtonFocusRingColor = SK_ColorWHITE;
 
@@ -104,9 +107,7 @@ class MdIPHBubbleButton : public MdTextButton {
       bg_color = theme->GetSystemButtonPressedColor(bg_color);
 
     SkColor stroke_color =
-        has_border_
-            ? theme->GetSystemColor(ui::NativeTheme::kColorId_ButtonBorderColor)
-            : kBubbleBackgroundColor;
+        has_border_ ? kBubbleButtonBorderColor : kBubbleBackgroundColor;
 
     SetBackground(CreateBackgroundFromPainter(
         Painter::CreateRoundRectWith1PxBorderPainter(bg_color, stroke_color,