Allow direct executors in cronet.

components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java

Index: components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java
diff --git a/components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java b/components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java
index 3b2601e61fc1aabdd14c754bdd8d77b72b7b6b3d..a8a8d454be1d33048a11f3cf75cef7e39886c673 100644
--- a/components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java
+++ b/components/cronet/android/java/src/org/chromium/net/impl/CronetUploadDataStream.java
@@ -300,26 +300,34 @@ public final class CronetUploadDataStream implements UploadDataSink {
     }
 
     /**
-     * Initializes upload length by getting it from data provider. Always called
-     * on executor thread to allow getLength() to block and/or report errors.
+     * Initializes upload length by getting it from data provider. Submits to
+     * the user's executor thread to allow getLength() to block and/or report errors.
      * If data provider throws an exception, then it is reported to the request.
      * No native calls to urlRequest are allowed as this is done before request
      * start, so native object may not exist.
      */
-    void initializeWithRequest(final CronetUrlRequest urlRequest) {
+    void initializeWithRequest(final CronetUrlRequest urlRequest, final Runnable callback) {
         synchronized (mLock) {
             mRequest = urlRequest;
-            mInWhichUserCallback = UserCallback.GET_LENGTH;
-        }
-        try {
-            mLength = mDataProvider.getLength();
-            mRemainingLength = mLength;
-        } catch (Throwable t) {
-            onError(t);
-        }
-        synchronized (mLock) {
-            mInWhichUserCallback = UserCallback.NOT_IN_CALLBACK;
         }
+        postTaskToExecutor(new Runnable() {
+            @Override
+            public void run() {
+                synchronized (mLock) {
+                    mInWhichUserCallback = UserCallback.GET_LENGTH;
+                }
+                try {
+                    mLength = mDataProvider.getLength();
+                    mRemainingLength = mLength;
+                } catch (Throwable t) {
+                    onError(t);
+                }
+                synchronized (mLock) {
+                    mInWhichUserCallback = UserCallback.NOT_IN_CALLBACK;
+                }
+                callback.run();
+            }
+        });
     }
 
     /**