Unified: Change background color opacity.

According to UX, background color opacity of UnifiedSystemTray was
dropped from 70% to 60%.

TEST=manual
BUG=863232

Change-Id: Idea912340d91e245cd6ca854b970c4d91e376057
Reviewed-on: https://chromium-review.googlesource.com/1173932Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582858}

ash/system/tray/tray_constants.h

@@ -134,9 +134,10 @@ extern const int kTrayPopupInkDropCornerRadius;
 extern const int kTrayPopupSystemInfoRowHeight;
 
 // The colors used when --enable-features=SystemTrayUnified flag is enabled.
-constexpr SkColor kUnifiedMenuBackgroundColor = SkColorSetRGB(0x20, 0x21, 0x24);
+constexpr SkColor kUnifiedMenuBackgroundColor =
+    SkColorSetARGB(0xf2, 0x20, 0x21, 0x24);
 constexpr SkColor kUnifiedMenuBackgroundColorWithBlur =
-    SkColorSetA(kUnifiedMenuBackgroundColor, 0xB3);
+    SkColorSetA(kUnifiedMenuBackgroundColor, 0x99);
 constexpr float kUnifiedMenuBackgroundBlur = 30.f;
 constexpr SkColor kUnifiedMenuTextColor = SkColorSetRGB(0xf1, 0xf3, 0xf4);
 constexpr SkColor kUnifiedMenuIconColor = SkColorSetRGB(0xf1, 0xf3, 0xf4);