Add some convenience constructors for Cronet in V2

- The need to pass a Clock is pretty much only for testing, so
  make the constructor that takes one package private + use
  the system clock for public constructors.
- Add default timeout values.
- Also make sure we set Content-Type in all license requests,
  since when using Cronet the stack requires it to be set.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131404298

library/src/main/java/com/google/android/exoplayer2/drm/HttpMediaDrmCallback.java

@@ -77,6 +77,8 @@ public byte[] executeKeyRequest(UUID uuid, KeyRequest request) throws Exception
   private byte[] executePost(String url, byte[] data, Map<String, String> requestProperties)
       throws IOException {
     HttpDataSource dataSource = dataSourceFactory.createDataSource();
+    // Note: This will be overridden by a Content-Type in requestProperties, if one is set.
+    dataSource.setRequestProperty("Content-Type", "application/octet-stream");
     if (requestProperties != null) {
       for (Map.Entry<String, String> requestProperty : requestProperties.entrySet()) {
         dataSource.setRequestProperty(requestProperty.getKey(), requestProperty.getValue());

library/src/main/java/com/google/android/exoplayer2/upstream/DefaultDataSourceFactory.java

@@ -69,8 +69,8 @@ public DefaultDataSourceFactory(Context context, String userAgent,
    */
   public DefaultDataSourceFactory(Context context, String userAgent,
       TransferListener<? super DataSource> listener, boolean allowCrossProtocolRedirects) {
-    this(context, userAgent, listener, DEFAULT_CONNECT_TIMEOUT_MILLIS,
-        DEFAULT_CONNECT_TIMEOUT_MILLIS, allowCrossProtocolRedirects);
+    this(context, userAgent, listener, DEFAULT_CONNECT_TIMEOUT_MILLIS, DEFAULT_READ_TIMEOUT_MILLIS,
+        allowCrossProtocolRedirects);
   }
 
   /**

library/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java

@@ -86,19 +86,19 @@ public class DefaultHttpDataSource implements HttpDataSource {
 
   /**
    * @param userAgent The User-Agent string that should be used.
-   * @param contentTypePredicate An optional {@link Predicate}. If a content type is
-   *     rejected by the predicate then a {@link HttpDataSource.InvalidContentTypeException} is
-   *     thrown from {@link #open(DataSpec)}.
+   * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
+   *     predicate then a {@link HttpDataSource.InvalidContentTypeException} is thrown from
+   *     {@link #open(DataSpec)}.
    */
   public DefaultHttpDataSource(String userAgent, Predicate<String> contentTypePredicate) {
     this(userAgent, contentTypePredicate, null);
   }
 
   /**
    * @param userAgent The User-Agent string that should be used.
-   * @param contentTypePredicate An optional {@link Predicate}. If a content type is
-   *     rejected by the predicate then a {@link HttpDataSource.InvalidContentTypeException} is
-   *     thrown from {@link #open(DataSpec)}.
+   * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
+   *     predicate then a {@link HttpDataSource.InvalidContentTypeException} is thrown from
+   *     {@link #open(DataSpec)}.
    * @param listener An optional listener.
    */
   public DefaultHttpDataSource(String userAgent, Predicate<String> contentTypePredicate,
@@ -109,9 +109,9 @@ public DefaultHttpDataSource(String userAgent, Predicate<String> contentTypePred
 
   /**
    * @param userAgent The User-Agent string that should be used.
-   * @param contentTypePredicate An optional {@link Predicate}. If a content type is
-   *     rejected by the predicate then a {@link HttpDataSource.InvalidContentTypeException} is
-   *     thrown from {@link #open(DataSpec)}.
+   * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
+   *     predicate then a {@link HttpDataSource.InvalidContentTypeException} is thrown from
+   *     {@link #open(DataSpec)}.
    * @param listener An optional listener.
    * @param connectTimeoutMillis The connection timeout, in milliseconds. A timeout of zero is
    *     interpreted as an infinite timeout.
@@ -126,9 +126,9 @@ public DefaultHttpDataSource(String userAgent, Predicate<String> contentTypePred
 
   /**
    * @param userAgent The User-Agent string that should be used.
-   * @param contentTypePredicate An optional {@link Predicate}. If a content type is
-   *     rejected by the predicate then a {@link HttpDataSource.InvalidContentTypeException} is
-   *     thrown from {@link #open(DataSpec)}.
+   * @param contentTypePredicate An optional {@link Predicate}. If a content type is rejected by the
+   *     predicate then a {@link HttpDataSource.InvalidContentTypeException} is thrown from
+   *     {@link #open(DataSpec)}.
    * @param listener An optional listener.
    * @param connectTimeoutMillis The connection timeout, in milliseconds. A timeout of zero is
    *     interpreted as an infinite timeout. Pass {@link #DEFAULT_CONNECT_TIMEOUT_MILLIS} to use