Add support for secure views.

Added the MotionEvent.FLAG_WINDOW_IS_OBSCURED flag which is set by the
input manager whenever another visible window is partly or wholly obscured
the target of a touch event so that applications can filter touches
accordingly.

Added a "filterTouchesWhenObscured" attribute to View which can be used to
enable filtering of touches when the view's window is obscured.

Change-Id: I936d9c85013fd2d77fb296a600528d30a29027d2

libs/ui/Input.cpp

@@ -129,6 +129,7 @@ void MotionEvent::initialize(
         int32_t deviceId,
         int32_t source,
         int32_t action,
+        int32_t flags,
         int32_t edgeFlags,
         int32_t metaState,
         float xOffset,
@@ -142,6 +143,7 @@ void MotionEvent::initialize(
         const PointerCoords* pointerCoords) {
     InputEvent::initialize(deviceId, source);
     mAction = action;
+    mFlags = flags;
     mEdgeFlags = edgeFlags;
     mMetaState = metaState;
     mXOffset = xOffset;