Make sure we cache the sampleTable again if using the caching datasource.

QA-impact: This fixes http streaming again which I broke about 2 days ago. The previously observed symptoms were stuttering playback of http streams (think YouTube) after a certain playback position.

Change-Id: I14050e3522ecd62c90d29310efdf508fdd2e87b5
related-to-bug: 3098873

media/libstagefright/MPEG4Extractor.cpp

@@ -498,7 +498,9 @@ status_t MPEG4Extractor::parseChunk(off_t *offset, int depth) {
             if (chunk_type == FOURCC('s', 't', 'b', 'l')) {
                 LOGV("sampleTable chunk is %d bytes long.", (size_t)chunk_size);
 
-                if (mDataSource->flags() & DataSource::kWantsPrefetching) {
+                if (mDataSource->flags()
+                        & (DataSource::kWantsPrefetching
+                            | DataSource::kIsCachingDataSource)) {
                     sp<MPEG4DataSource> cachedSource =
                         new MPEG4DataSource(mDataSource);