Bug 1172382 - Enable AccessibleCaret on B2G. r=roc

The new AccessibleCaret replaces TouchCaret and SelectionCarets. Disable
them accordingly.

--HG--
extra : commitid : H2bSIbLfEXs

b2g/app/b2g.js

@@ -1100,11 +1100,14 @@ pref("dom.wakelock.enabled", true);
 // Enable webapps add-ons
 pref("dom.apps.customization.enabled", true);
 
-// Enable touch caret by default
-pref("touchcaret.enabled", true);
+// Original caret implementation on collapsed selection.
+pref("touchcaret.enabled", false);
 
-// Enable selection caret by default
-pref("selectioncaret.enabled", true);
+// Original caret implementation on non-collapsed selection.
+pref("selectioncaret.enabled", false);
+
+// New implementation to unify touch-caret and selection-carets.
+pref("layout.accessiblecaret.enabled", true);
 
 // Enable sync and mozId with Firefox Accounts.
 pref("services.sync.fxaccounts.enabled", true);

modules/libpref/init/all.js

@@ -4739,7 +4739,7 @@ pref("browser.trackingprotection.gethashURL", "https://tracking.services.mozilla
 // Turn off Spatial navigation by default.
 pref("snav.enabled", false);
 
-// Turn off touch caret by default.
+// Original caret implementation on collapsed selection.
 pref("touchcaret.enabled", false);
 
 // This will inflate the size of the touch caret frame when checking if user
@@ -4751,7 +4751,7 @@ pref("touchcaret.inflatesize.threshold", 40);
 // In milliseconds. (0 means disable this feature)
 pref("touchcaret.expiration.time", 3000);
 
-// Turn off selection caret by default
+// Original caret implementation on non-collapsed selection.
 pref("selectioncaret.enabled", false);
 
 // This will inflate size of selection caret frame when we checking if