+2014-09-23 Dean Jackson <dino@apple.com>
+
+ [Yosemite] Button text doesn't go white while pushing the button, like it does for real buttons
+ https://bugs.webkit.org/show_bug.cgi?id=137054
+ rdar://problem/17559038
+
+ Reviewed by Sam Weinig.
+
+ On Yosemite and above, system buttons paint with white-ish text when they
+ are pressed. Since this isn't exposed by API, I've hardcoded the value
+ into RenderThemeMac.
+
+ The actual state is exposed by adding a :active rule to html.css that
+ uses a new CSSValueKeyword: ActiveButtonText.
+
+ Unfortunately I can't find a way to test this, because the active state isn't
+ testable. We should really expose the Inspector's forcePseudoState function into
+ window.internals.
+
+ * css/CSSValueKeywords.in: Add "activebuttontext".
+ * css/html.css:
+ (input[type="button"]:active, input[type="submit"]:active, input[type="reset"]:active, input[type="file"]::-webkit-file-upload-button:active, button:active): New rule for active
+ button elements.
+ * rendering/RenderTheme.cpp:
+ (WebCore::RenderTheme::systemColor): Handle CSSValueActivebuttontext as black.
+ * rendering/RenderThemeMac.mm:
+ (WebCore::RenderThemeMac::systemColor): Handle CSSValueActivebuttontext as
+ white with 75% opacity.
+