Update generationId on bitmaps when decoded into by BitmapRegionDecoder

bug:18921087

This fixes issues where bitmaps are cached as textures, and not
reuploaded when reused by BitmapRegionDecoder, showing stale content.

Change-Id: I7626fd6acd36d8e38723689734855ce9154eb8c8

core/jni/android/graphics/BitmapRegionDecoder.cpp

@@ -242,6 +242,7 @@ static jobject nativeDecodeRegion(JNIEnv* env, jobject, jlong brdHandle,
     }
 
     if (tileBitmap != NULL) {
+        bitmap->notifyPixelsChanged();
         return tileBitmap;
     }