Add :indeterminate pseudo class support for radio button input

Source/platform/mac/ThemeMac.mm

Index: Source/platform/mac/ThemeMac.mm
diff --git a/Source/platform/mac/ThemeMac.mm b/Source/platform/mac/ThemeMac.mm
index 4e702e1b7071e584c8c439a3175eed4eda8ffcbb..9d37a4f19e3264f0028eb73136ff5d61e73e04bb 100644
--- a/Source/platform/mac/ThemeMac.mm
+++ b/Source/platform/mac/ThemeMac.mm
@@ -349,6 +349,8 @@ static NSButtonCell *radio(ControlStates states, const IntRect& zoomedRect, floa
     setControlSize(radioCell, radioSizes(), zoomedRect.size(), zoomFactor);
 
     // Update the various states we respond to.
+    // Cocoa draws NSMixedState NSRadioButton as NSOnState so we don't want that.
+    states &= ~IndeterminateControlState;

[tkent, 2014/07/15 01:31:50]

Do we have a pixel test for indeterminate radio buttons?
If not, we should add it to fast/forms/radio/radio-appearance-basic.html.

[keishi, 2014/07/15 03:05:30]

All elements in radio-appearance-basic.html are not in a radio button group so
the unchecked ones have the indeterminate appearance. I added a not
indeterminate not checked test to radio-appearance-basic.html.

     updateStates(radioCell, states);
     
     return radioCell;