Partial revert of DRM fixes

```-------------------------------
Original change description:

DRM fixes

- Parse multiple kids from default_KID. It's specified as a whitespace
  separated list of UUIDs rather than a single UUID.
- Opportunistically proceed with playback in cases where the manifest
  only defines a single SchemeData with the common PSSH UUID. In such
  cases the manifest isn't saying anything about which specific DRM
  schemes it supports.

Issue: #3630
```

----------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=181137621

RELEASENOTES.md

@@ -29,9 +29,6 @@
   positions.
   * Note: `SeekParameters` are only currently effective when playing
     `ExtractorMediaSource`s (i.e. progressive streams).
-* DRM: Optimistically attempt playback of DRM protected content that does not
-  declare scheme specific init data
-  ([#3630](https://github.com/google/ExoPlayer/issues/3630)).
 * DASH: Support DASH manifest EventStream elements.
 * HLS: Add opt-in support for chunkless preparation in HLS. This allows an
   HLS source to finish preparation without downloading any chunks, which can

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManager.java

@@ -23,7 +23,6 @@ import android.os.Message;
 import android.support.annotation.IntDef;
 import android.support.annotation.NonNull;
 import android.text.TextUtils;
-import android.util.Log;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.drm.DefaultDrmSession.ProvisioningManager;
@@ -109,7 +108,6 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
   /** Number of times to retry for initial provisioning and key request for reporting error. */
   public static final int INITIAL_DRM_REQUEST_RETRY_COUNT = 3;
 
-  private static final String TAG = "DrmSessionManager";
   private static final String CENC_SCHEME_MIME_TYPE = "cenc";
 
   private final UUID uuid;
@@ -353,15 +351,9 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
   public boolean canAcquireSession(@NonNull DrmInitData drmInitData) {
     SchemeData schemeData = getSchemeData(drmInitData, uuid, true);
     if (schemeData == null) {
-      if (drmInitData.schemeDataCount == 1 && drmInitData.get(0).matches(C.COMMON_PSSH_UUID)) {
-        // Assume scheme specific data will be added before the session is opened.
-        Log.w(
-            TAG, "DrmInitData only contains common PSSH SchemeData. Assuming support for: " + uuid);
-      } else {
       // No data for this manager's scheme.
       return false;
     }
-    }
     String schemeType = drmInitData.schemeType;
     if (schemeType == null || C.CENC_TYPE_cenc.equals(schemeType)) {
       // If there is no scheme information, assume patternless AES-CTR.