Fix accessibility contrast of Quick Settings "Connected" subtext

This changes the color of "Connected" subtext from GoogleGreenDark600 to
kTextColorPositive which resolves to GoogleGreen300 in dark mode.

Bug: 1134227
Change-Id: I6946e86b50fe9428164341e6f907bb64616e59ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2485337Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Sonny Sasaka <sonnysasaka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818998}

ash/system/tray/tray_popup_item_style.cc

@@ -71,7 +71,8 @@ SkColor TrayPopupItemStyle::GetTextColor() const {
     case ColorStyle::DISABLED:
       return SkColorSetA(kBaseTextColor, kDisabledAlpha);
     case ColorStyle::CONNECTED:
-      return gfx::kGoogleGreenDark600;
+      return AshColorProvider::Get()->GetContentLayerColor(
+          AshColorProvider::ContentLayerType::kTextColorPositive);
   }
   NOTREACHED();
   return gfx::kPlaceholderColor;