Follow ARIA spec guidelines for role=button with aria-pressed.

webkit/glue/webkit_strings.grd

Index: webkit/glue/webkit_strings.grd
diff --git a/webkit/glue/webkit_strings.grd b/webkit/glue/webkit_strings.grd
index 949d04d4cacec808854c75b4b45027443de9a623..37efcad7bb103010b2e851372eecfd02be448935 100644
--- a/webkit/glue/webkit_strings.grd
+++ b/webkit/glue/webkit_strings.grd
@@ -347,6 +347,9 @@ below:
       <message name="IDS_AX_ROLE_STEPPER" desc="accessibility role description for a stepper - a control where you can use up/down arrows to increment or decrement it. The name 'stepper' is how this user interface element is described by VoiceOver on Mac OS X; the translation should be consistent with VoiceOver.">
         stepper
       </message>
+      <message name="IDS_AX_ROLE_TOGGLE_BUTTON" desc="accessibility role description for a toggle button">
+        toggle button
+      </message>
 
       <message name="IDS_AX_BUTTON_ACTION_VERB" desc="Verb stating the action that will occur when a button is pressed, as used by accessibility.">
         press