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 interface Cache {
       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 @@ import javax.crypto.spec.SecretKeySpec;
    *
    * @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 @@ import javax.crypto.spec.SecretKeySpec;
         throw new IllegalStateException(e); // Should never happen.
       }
     } else {
+      Assertions.checkState(!encrypt);
       cipher = null;
       secretKeySpec = null;
     }
@@ -259,10 +261,8 @@ import javax.crypto.spec.SecretKeySpec;
           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 @@ import javax.crypto.spec.SecretKeySpec;
       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 final class SimpleCache implements Cache {
    * @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 final class SimpleCache implements Cache {
       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 final class SimpleCache implements Cache {
   @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 @@ public final class SimpleCache implements Cache {
   /**
    * 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 @@ public final class SimpleCache implements Cache {
     }
 
     index.removeEmpty();
-    index.store();
+    // Don't call index.store() here so initialization doesn't fail because of write issues.
   }
 
   /**