[Picture in Picture] Make media controls icon images black.

The background is kept white.

Bug: 863702
Change-Id: Ia8d0f2bb8f9c1a0263c527906f076a1fa78f5823
Reviewed-on: https://chromium-review.googlesource.com/1137752Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575336}

chrome/browser/ui/views/overlay/overlay_window_views.cc

@@ -45,7 +45,7 @@ const int kMinPlayPauseButtonSize = 48;
 
 // Colors for the control buttons.
 SkColor kBgColor = SK_ColorWHITE;
-SkColor kControlIconColor = gfx::kChromeIconGrey;
+SkColor kControlIconColor = SK_ColorBLACK;
 }  // namespace
 
 // OverlayWindow implementation of NonClientFrameView.