Exception when performing the global gestrue to enable accessibility.

1. If there is a non-speaking accessibility service installed and the
   global gesture is performed an exception is thrown since an attempt
   is made to modify the list with services returned by the accessibility
   manager (to remove the non-speaking ones) but this list is immutable.
   Now the returned services are put into a mutable list before removing
   the non-speaking ones.

bug:7280996

Change-Id: I2852a3e169c1d34d942b50fb439e0961394c92bc

Author: sganov

policy/src/com/android/internal/policy/impl/EnableAccessibilityController.java

@@ -40,6 +40,7 @@
 
 import com.android.internal.R;
 
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
@@ -131,8 +132,9 @@ public static boolean canEnableAccessibilityViaGesture(Context context) {
 
     private static List<AccessibilityServiceInfo> getInstalledSpeakingAccessibilityServices(
             Context context) {
-        List<AccessibilityServiceInfo> services = AccessibilityManager.getInstance(
-                context).getInstalledAccessibilityServiceList();
+        List<AccessibilityServiceInfo> services = new ArrayList<AccessibilityServiceInfo>();
+        services.addAll(AccessibilityManager.getInstance(context)
+                .getInstalledAccessibilityServiceList());
         Iterator<AccessibilityServiceInfo> iterator = services.iterator();
         while (iterator.hasNext()) {
             AccessibilityServiceInfo service = iterator.next();