Fix unnecessary CachedContentIndex store() calls

First fix, prevents forced rewriting when cipher is set but encrypt is
false.

Second, removes the store() call in SimpleCache.initialize() so
initialization doesn't fail because of CachedContentIndex write issues.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174450586

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/Cache.java

@@ -72,7 +72,7 @@ public CacheException(String message) {
       super(message);
     }
 
-    public CacheException(IOException cause) {
+    public CacheException(Throwable cause) {
       super(cause);
     }
 

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java

@@ -92,7 +92,8 @@ public CachedContentIndex(File cacheDir, byte[] secretKey) {
    *
    * @param cacheDir Directory where the index file is kept.
    * @param secretKey 16 byte AES key for reading, and optionally writing, the cache index.
-   * @param encrypt When false, a plaintext index will be written.
+   * @param encrypt Whether the index will be encrypted when written. Must be false if {@code
+   *     secretKey} is null.
    */
   public CachedContentIndex(File cacheDir, byte[] secretKey, boolean encrypt) {
     this.encrypt = encrypt;
@@ -105,6 +106,7 @@ public CachedContentIndex(File cacheDir, byte[] secretKey, boolean encrypt) {
         throw new IllegalStateException(e); // Should never happen.
       }
     } else {
+      Assertions.checkState(!encrypt);
       cipher = null;
       secretKeySpec = null;
     }
@@ -259,10 +261,8 @@ private boolean readFile() {
           throw new IllegalStateException(e);
         }
         input = new DataInputStream(new CipherInputStream(inputStream, cipher));
-      } else {
-        if (cipher != null) {
-          changed = true; // Force index to be rewritten encrypted after read.
-        }
+      } else if (encrypt) {
+        changed = true; // Force index to be rewritten encrypted after read.
       }
 
       int count = input.readInt();
@@ -300,11 +300,10 @@ private void writeFile() throws CacheException {
       output = new DataOutputStream(bufferedOutputStream);
       output.writeInt(VERSION);
 
-      boolean writeEncrypted = encrypt && cipher != null;
-      int flags = writeEncrypted ? FLAG_ENCRYPTED_INDEX : 0;
+      int flags = encrypt ? FLAG_ENCRYPTED_INDEX : 0;
       output.writeInt(flags);
 
-      if (writeEncrypted) {
+      if (encrypt) {
         byte[] initializationVector = new byte[16];
         new Random().nextBytes(initializationVector);
         output.write(initializationVector);

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java

@@ -37,7 +37,6 @@ public final class SimpleCache implements Cache {
   private final CachedContentIndex index;
   private final HashMap<String, ArrayList<Listener>> listeners;
   private long totalSpace = 0;
-  private CacheException initializationException;
 
   /**
    * Constructs the cache. The cache will delete any unrecognized files from the directory. Hence
@@ -71,7 +70,8 @@ public SimpleCache(File cacheDir, CacheEvictor evictor, byte[] secretKey) {
    * @param evictor The evictor to be used.
    * @param secretKey If not null, cache keys will be stored encrypted on filesystem using AES/CBC.
    *     The key must be 16 bytes long.
-   * @param encrypt When false, a plaintext index will be written.
+   * @param encrypt Whether the index will be encrypted when written. Must be false if {@code
+   *     secretKey} is null.
    */
   public SimpleCache(File cacheDir, CacheEvictor evictor, byte[] secretKey, boolean encrypt) {
     this(cacheDir, evictor, new CachedContentIndex(cacheDir, secretKey, encrypt));
@@ -98,11 +98,7 @@ public SimpleCache(File cacheDir, CacheEvictor evictor, byte[] secretKey, boolea
       public void run() {
         synchronized (SimpleCache.this) {
           conditionVariable.open();
-          try {
-            initialize();
-          } catch (CacheException e) {
-            initializationException = e;
-          }
+          initialize();
           SimpleCache.this.evictor.onCacheInitialized();
         }
       }
@@ -169,10 +165,6 @@ public synchronized SimpleCacheSpan startReadWrite(String key, long position)
   @Override
   public synchronized SimpleCacheSpan startReadWriteNonBlocking(String key, long position)
       throws CacheException {
-    if (initializationException != null) {
-      throw initializationException;
-    }
-
     SimpleCacheSpan cacheSpan = getSpan(key, position);
 
     // Read case.
@@ -270,7 +262,7 @@ private SimpleCacheSpan getSpan(String key, long position) throws CacheException
   /**
    * Ensures that the cache's in-memory representation has been initialized.
    */
-  private void initialize() throws CacheException {
+  private void initialize() {
     if (!cacheDir.exists()) {
       cacheDir.mkdirs();
       return;
@@ -296,7 +288,7 @@ private void initialize() throws CacheException {
     }
 
     index.removeEmpty();
-    index.store();
+    // Don't call index.store() here so initialization doesn't fail because of write issues.
   }
 
   /**