Don't install focus rings on hover buttons

Since these focus on hover, we pretty much never want to do this (..right?)

Bug: 874913
Change-Id: I68c129184e0cf6e5895923696158b10cbefd3adc
Reviewed-on: https://chromium-review.googlesource.com/1177914Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583762}

chrome/browser/ui/views/hover_button.cc

@@ -72,6 +72,7 @@ HoverButton::HoverButton(views::ButtonListener* button_listener,
       icon_view_(nullptr),
       secondary_icon_view_(nullptr),
       listener_(button_listener) {
+  SetInstallFocusRingOnFocus(false);
   SetFocusBehavior(FocusBehavior::ALWAYS);
   SetFocusPainter(nullptr);