Deprecate MediaExtractor.setMediaCas

- There is no evidence of usage, after
  checking with all known stakeholders.
- We are aware of bugs that were never
  detected by users (b/193267732).
- The successor (MediaCasV2) is already available
  as a system API (under android.media.tv.tuner,
  including the Descrambler class).

Deprecation has a role in the long term MediaExtractor
codebase convergence.

Test: Built the tree.
Bug: 201414083
Change-Id: If7a6f160a007ab2db9e55a1ad003a948e6668b58

core/api/current.txt

@@ -22649,7 +22649,7 @@ package android.media {
     method public void setDataSource(@NonNull java.io.FileDescriptor) throws java.io.IOException;
     method public void setDataSource(@NonNull java.io.FileDescriptor, long, long) throws java.io.IOException;
     method public void setLogSessionId(@NonNull android.media.metrics.LogSessionId);
-    method public void setMediaCas(@NonNull android.media.MediaCas);
+    method @Deprecated public void setMediaCas(@NonNull android.media.MediaCas);
     method public void unselectTrack(int);
     field public static final int SAMPLE_FLAG_ENCRYPTED = 2; // 0x2
     field public static final int SAMPLE_FLAG_PARTIAL_FRAME = 4; // 0x4

media/java/android/media/MediaExtractor.java

@@ -250,15 +250,10 @@ public final class MediaExtractor {
             @NonNull FileDescriptor fd, long offset, long length) throws IOException;
 
     /**
-     * Sets the MediaCas instance to use. This should be called after a
-     * successful setDataSource() if at least one track reports mime type
-     * of {@link android.media.MediaFormat#MIMETYPE_AUDIO_SCRAMBLED}
-     * or {@link android.media.MediaFormat#MIMETYPE_VIDEO_SCRAMBLED}.
-     * Stream parsing will not proceed until a valid MediaCas object
-     * is provided.
-     *
-     * @param mediaCas the MediaCas object to use.
+     * @deprecated Use the {@code Descrambler} system API instead, or DRM public APIs like
+     *             {@link MediaDrm}.
      */
+    @Deprecated
     public final void setMediaCas(@NonNull MediaCas mediaCas) {
         mMediaCas = mediaCas;
         nativeSetMediaCas(mediaCas.getBinder());