Clean up handling of encrypted samples in fmp4/webm extractors.

- The fmp4 extractor was reading from sampleEncryptionData even
  for not-encrypted samples, which I'm pretty sure isn't right.
  Fixed this. For all encrypted content I've seen, this change
  will be a no-op because isEncrypted is always true if there's
  an encryptionBox present.
- Made webm extractor only set cryptoInfo if isEncrypted is true.
- Align variable naming in the two extractors, for clarity.

library/src/main/java/com/google/android/exoplayer/chunk/parser/mp4/FragmentedMp4Extractor.java

@@ -799,8 +799,11 @@ public final class FragmentedMp4Extractor implements Extractor {
   private void readSampleEncryptionData(ParsableByteArray sampleEncryptionData, SampleHolder out) {
     TrackEncryptionBox encryptionBox =
         track.sampleDescriptionEncryptionBoxes[fragmentRun.sampleDescriptionIndex];
+    if (!encryptionBox.isEncrypted) {
+      return;
+    }
+
     byte[] keyId = encryptionBox.keyId;
-    boolean isEncrypted = encryptionBox.isEncrypted;
     int vectorSize = encryptionBox.initializationVectorSize;
     boolean subsampleEncryption = fragmentRun.sampleHasSubsampleEncryptionTable[sampleIndex];
 
@@ -828,11 +831,10 @@ public final class FragmentedMp4Extractor implements Extractor {
       clearDataSizes[0] = 0;
       encryptedDataSizes[0] = fragmentRun.sampleSizeTable[sampleIndex];
     }
+
     out.cryptoInfo.set(subsampleCount, clearDataSizes, encryptedDataSizes, keyId, vector,
-        isEncrypted ? MediaCodec.CRYPTO_MODE_AES_CTR : MediaCodec.CRYPTO_MODE_UNENCRYPTED);
-    if (isEncrypted) {
-      out.flags |= MediaExtractor.SAMPLE_FLAG_ENCRYPTED;
-    }
+        MediaCodec.CRYPTO_MODE_AES_CTR);
+    out.flags |= MediaExtractor.SAMPLE_FLAG_ENCRYPTED;
   }
 
 }

library/src/main/java/com/google/android/exoplayer/chunk/parser/webm/WebmExtractor.java

@@ -486,29 +486,30 @@ public final class WebmExtractor implements Extractor {
             throw new ParserException("Extension bit is set in signal byte");
           }
           boolean isEncrypted = (signalByte[0] & 0x01) == 0x01;
-          byte[] iv = null;
           if (isEncrypted) {
+            byte[] iv = null;
             iv = sampleHolder.cryptoInfo.iv;
             if (iv == null || iv.length != BLOCK_COUNTER_SIZE) {
               iv = new byte[BLOCK_COUNTER_SIZE];
             }
             reader.readBytes(inputStream, iv, 8); // The container has only 8 bytes of IV.
             sampleHolder.size -= 8;
+
+            int[] clearDataSizes = sampleHolder.cryptoInfo.numBytesOfClearData;
+            if (clearDataSizes == null || clearDataSizes.length < 1) {
+              clearDataSizes = new int[1];
+            }
+            int[] encryptedDataSizes = sampleHolder.cryptoInfo.numBytesOfEncryptedData;
+            if (encryptedDataSizes == null || encryptedDataSizes.length < 1) {
+              encryptedDataSizes = new int[1];
+            }
+            clearDataSizes[0] = 0;
+            encryptedDataSizes[0] = sampleHolder.size;
+
+            sampleHolder.cryptoInfo.set(1, clearDataSizes, encryptedDataSizes,
+                encryptionKeyId, iv, MediaCodec.CRYPTO_MODE_AES_CTR);
             sampleHolder.flags |= MediaExtractor.SAMPLE_FLAG_ENCRYPTED;
           }
-          int[] numBytesOfClearData = sampleHolder.cryptoInfo.numBytesOfClearData;
-          if (numBytesOfClearData == null || numBytesOfClearData.length != 1) {
-            numBytesOfClearData = new int[1];
-          }
-          numBytesOfClearData[0] = isEncrypted ? 0 : sampleHolder.size;
-          int[] numBytesOfEncryptedData = sampleHolder.cryptoInfo.numBytesOfEncryptedData;
-          if (numBytesOfEncryptedData == null || numBytesOfEncryptedData.length != 1) {
-            numBytesOfEncryptedData = new int[1];
-          }
-          numBytesOfEncryptedData[0] = isEncrypted ? sampleHolder.size : 0;
-          sampleHolder.cryptoInfo.set(
-              1, numBytesOfClearData, numBytesOfEncryptedData, encryptionKeyId, iv,
-              isEncrypted ? MediaCodec.CRYPTO_MODE_AES_CTR : MediaCodec.CRYPTO_MODE_UNENCRYPTED);
         }
 
         if (sampleHolder.data == null || sampleHolder.data.capacity() < sampleHolder.size) {