TouchExplorer crashes if there is incative pointer while dragging.

The TouchExplorer was not taking into account the case with incative
pointers while dragging. If one puts a finger down and then perfroms
a dragging gestore the explorer tries to inject UP event for the end
of the gesture upon every of the two dragging pointers going up instead
only for one the first went up.

bug:5476098

Change-Id: I20d2dd7bde7e016b0678a35d14cd068d9ff37023

Author: sganov

services/java/com/android/server/accessibility/TouchExplorer.java

@@ -487,8 +487,16 @@ private void handleMotionEventStateDragging(MotionEvent event, int policyFlags)
                 }
             } break;
             case MotionEvent.ACTION_POINTER_UP: {
-                // Send an event to the end of the drag gesture.
-                sendMotionEvent(event, MotionEvent.ACTION_UP, pointerIdBits, policyFlags);
+                final int activePointerCount = mPointerTracker.getActivePointerCount();
+                switch (activePointerCount) {
+                    case 1: {
+                        // Send an event to the end of the drag gesture.
+                        sendMotionEvent(event, MotionEvent.ACTION_UP, pointerIdBits, policyFlags);
+                    } break;
+                    default: {
+                        mCurrentState = STATE_TOUCH_EXPLORING;
+                    }
+                }
              } break;
             case MotionEvent.ACTION_UP: {
                 mCurrentState = STATE_TOUCH_EXPLORING;