Adjust menu border colors for light and dark mode.

The light mode color (#BABABA) dates back well before Material Design (v1), and
doesn't seem to have an updated spec anywhere.  kGoogleGrey300 matches button
borders.  (Dialog borders use a different color that's based on alpha-blending
black, and has a surrounding shadow, so it doesn't seem quite as parallel.)

Using kGoogleGrey800 in dark mode happens to provide the same contrast against
the menu background (1.37) as GG300 does in light mode.

Bug: 995442
Change-Id: If8c668ad58c90f4a82dd1869219330b811894fca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1762479
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689199}

ui/native_theme/common_theme.cc

@@ -82,6 +82,8 @@ SkColor GetAuraColor(NativeTheme::ColorId color_id,
         return gfx::kGoogleGrey200;
       case NativeTheme::kColorId_FocusedMenuItemBackgroundColor:
         return SkColorSetA(SK_ColorWHITE, 0x29);
+      case NativeTheme::kColorId_MenuBorderColor:
+        return gfx::kGoogleGrey800;
       case NativeTheme::kColorId_MenuSeparatorColor:
         return SkColorSetA(gfx::kGoogleGrey800, 0xCC);
       case NativeTheme::kColorId_MenuBackgroundColor:
@@ -245,7 +247,7 @@ SkColor GetAuraColor(NativeTheme::ColorId color_id,
     case NativeTheme::kColorId_EnabledMenuItemForegroundColor:
       return SK_ColorBLACK;
     case NativeTheme::kColorId_MenuBorderColor:
-      return SkColorSetRGB(0xBA, 0xBA, 0xBA);
+      return gfx::kGoogleGrey300;
     case NativeTheme::kColorId_MenuSeparatorColor:
       return gfx::kGoogleGrey200;
     case NativeTheme::kColorId_MenuBackgroundColor: