Client app crashes if accessibility service uses invalid focus type.

1. If an accessibility service uses an invalid focus type argument
   when trying to find where focus is the queried application crashes.
   The same happens if the serivce calls focus search with an invalid
   derection. While we need the argument check in the controller that
   runs in the app process the accessibility service has to be the
   palace where an exception is thown for the invalid argument so
   the developer can fix his code.:

bug:6508797

Change-Id: Ib0d74f374fa60ee8fd6117f11c23af34f6c26ad3

Author: sganov

core/java/android/view/accessibility/AccessibilityNodeInfo.java

@@ -443,6 +443,7 @@ public void setSource(View root, int virtualDescendantId) {
      */
     public AccessibilityNodeInfo findFocus(int focus) {
         enforceSealed();
+        enforceValidFocusType(focus);
         if (!canPerformRequestOverConnection(mSourceNodeId)) {
             return null;
         }
@@ -472,6 +473,7 @@ public AccessibilityNodeInfo findFocus(int focus) {
      */
     public AccessibilityNodeInfo focusSearch(int direction) {
         enforceSealed();
+        enforceValidFocusDirection(direction);
         if (!canPerformRequestOverConnection(mSourceNodeId)) {
             return null;
         }
@@ -1330,6 +1332,36 @@ protected void enforceSealed() {
         }
     }
 
+    private void enforceValidFocusDirection(int direction) {
+        switch (direction) {
+            case View.FOCUS_DOWN:
+            case View.FOCUS_UP:
+            case View.FOCUS_LEFT:
+            case View.FOCUS_RIGHT:
+            case View.FOCUS_FORWARD:
+            case View.FOCUS_BACKWARD:
+            case View.ACCESSIBILITY_FOCUS_DOWN:
+            case View.ACCESSIBILITY_FOCUS_UP:
+            case View.ACCESSIBILITY_FOCUS_LEFT:
+            case View.ACCESSIBILITY_FOCUS_RIGHT:
+            case View.ACCESSIBILITY_FOCUS_FORWARD:
+            case View.ACCESSIBILITY_FOCUS_BACKWARD:
+                return;
+            default:
+                throw new IllegalArgumentException("Unknown direction: " + direction);
+        }
+    }
+
+    private void enforceValidFocusType(int focusType) {
+        switch (focusType) {
+            case FOCUS_INPUT:
+            case FOCUS_ACCESSIBILITY:
+                return;
+            default:
+                throw new IllegalArgumentException("Unknown focus type: " + focusType);
+        }
+    }
+
     /**
      * Enforces that this instance is not sealed.
      *