Tab strip separator contrast -> 2.5

Bug: 929866
Change-Id: I9d00bbc56040fbeb1973cda37e28af1507842043
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1509359Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638755}

chrome/browser/ui/views/tabs/tab_strip.cc

@@ -2250,7 +2250,7 @@ void TabStrip::UpdateContrastRatioValues() {
 
   const SkColor inactive_fg = GetTabForegroundColor(TAB_INACTIVE, inactive_bg);
   // The contrast ratio for the separator between inactive tabs.
-  constexpr float kTabSeparatorContrast = 3.0f;
+  constexpr float kTabSeparatorContrast = 2.5f;
   const SkAlpha separator_alpha = get_alpha(inactive_fg, kTabSeparatorContrast);
   separator_color_ =
       color_utils::AlphaBlend(inactive_fg, inactive_bg, separator_alpha);