Bug 1311402 - Dark theme scrollbars need to also match root scrollbars. r=ntim

MozReview-Commit-ID: 2aWKBiWgBMm

--HG--
extra : rebase_source : ae2ffec87753785cda11ec12ea2f898813b51278

devtools/client/themes/floating-scrollbars-dark-theme.css

@@ -15,6 +15,7 @@
   padding: 2px;
 }
 
+*|*:root[platform="mac"] > scrollbar,
 *|*:root[platform="mac"] *|*:not(html|select) > scrollbar {
   border: none;
 }
@@ -40,10 +41,15 @@
   border-radius: 3px !important;
 }
 
+*|*:root[platform="mac"] > scrollbar slider,
 *|*:root[platform="mac"] *|*:not(html|select) > scrollbar slider {
   -moz-appearance: none !important;
 }
 
+*|*:root[platform="win"] > scrollbar scrollbarbutton,
+*|*:root[platform="linux"] > scrollbar scrollbarbutton,
+*|*:root[platform="win"] > scrollbar gripper,
+*|*:root[platform="linux"] > scrollbar gripper,
 *|*:root[platform="win"] *|*:not(html|select) > scrollbar scrollbarbutton,
 *|*:root[platform="linux"] *|*:not(html|select) > scrollbar scrollbarbutton,
 *|*:root[platform="win"] *|*:not(html|select) > scrollbar gripper,