Add notifyPixelsChanged() call to NDK unlockPixels().

Without this call, the NDK bitmap methods don't work in
hardware-accelerated mode ( http://b/5017848 ).

Change-Id: Icae6975757c9c9e83c0e9fc132161aa3004f8f28

native/graphics/jni/bitmap.cpp

@@ -88,6 +88,12 @@ int AndroidBitmap_unlockPixels(JNIEnv* env, jobject jbitmap) {
         return ANDROID_BITMAP_RESULT_JNI_EXCEPTION;
     }
 
+    // notifyPixelsChanged() needs be called to apply writes to GL-backed
+    // bitmaps.  Note that this will slow down read-only accesses to the
+    // bitmaps, but the NDK methods are primarily intended to be used for
+    // writes.
+    bm->notifyPixelsChanged();
+
     bm->unlockPixels();
     return ANDROID_BITMAP_RESUT_SUCCESS;
 }