Move some accessibility methods, enums and interfaces into the content/public API.

content/common/view_message_enums.h

Index: content/common/view_message_enums.h
diff --git a/content/common/view_message_enums.h b/content/common/view_message_enums.h
index 59a6da11b0aed6f04f35803b5ecde6422763356d..662920230c0443eacb638815b87a1d9f2f2cf793 100644
--- a/content/common/view_message_enums.h
+++ b/content/common/view_message_enums.h
@@ -53,19 +53,4 @@ struct ViewMsg_Navigate_Type {
   };
 };
 
-enum AccessibilityMode {
-  // WebKit accessibility is off and no accessibility information is
-  // sent from the renderer to the browser process.
-  AccessibilityModeOff,
-
-  // WebKit accessibility is on, but only limited information about
-  // editable text nodes is sent to the browser process. Useful for
-  // implementing limited UIA on tablets.
-  AccessibilityModeEditableTextOnly,
-
-  // WebKit accessibility is on, and the full accessibility tree is synced
-  // to the browser process. Useful for screen readers and magnifiers.
-  AccessibilityModeComplete,
-};
-
 #endif  // CONTENT_COMMON_VIEW_MESSAGES_ENUMS_H_