Bug 1393084 - Update page text selection handlers. r=nechen

:root {

	--color_background_highlight: rgba(255, 149, 0, 0.6);

	--color_background_highlight: rgba(10, 132, 255, 0.6); /*matched to action_accent in java codebase*/

	--color_background_highlight_overlay: rgba(171, 171, 171, 0.5);

	--color_text_highlight: #000;