Fix bug #15897505 Talk back state shows "off" while the talk back is still enabled.

- we were missing the update of the TextView from the SwitchBar so provide a new
setCheckedInternal() method that is doing the TextView and Switch update at the
same time

Change-Id: I6dd9c472a386bb534a58fbf5cf82d9d01fa74f6c

src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java

@@ -35,7 +35,7 @@ public class ToggleScreenMagnificationPreferenceFragment
         mToggleSwitch.setOnBeforeCheckedChangeListener(new OnBeforeCheckedChangeListener() {
                 @Override
             public boolean onBeforeCheckedChanged(ToggleSwitch toggleSwitch, boolean checked) {
-                toggleSwitch.setCheckedInternal(checked);
+                mSwitchBar.setCheckedInternal(checked);
                 getArguments().putBoolean(AccessibilitySettings.EXTRA_CHECKED, checked);
                 onPreferenceToggled(mPreferenceKey, checked);
                 return false;