Fix ANRs due to Widevine DRM plugin sniff taking too long.

Add a Widevine-specific format sniffer to avoid having to
refetch data from the remote server.

related-to-bug: 5725548

Change-Id: I622e39930f8d243111e4731557b0df17c4e2651d

proprietary/wvm/include/WVMExtractorImpl.h

@@ -31,7 +31,7 @@
 namespace android {
 
 WVMLoadableExtractor *GetInstance(sp<DataSource> dataSource);
-
+bool IsWidevineMedia(sp<DataSource> dataSource);
 
 class WVMMediaSource;
 class WVMFileSource;