Initial implementation of Cronet Async API.

components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java

Index: components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java
diff --git a/components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java b/components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java
index 2b08e7d99472e8a07a813d78446f6f608797ebb8..4cf94476c94284f8b2877b67331e984b5481dd00 100644
--- a/components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java
+++ b/components/cronet/android/java/src/org/chromium/net/UrlRequestFactory.java
@@ -4,13 +4,21 @@
 
 package org.chromium.net;
 
+import android.content.Context;
+import android.util.Log;
+
+import java.lang.reflect.Constructor;
 import java.util.concurrent.Executor;
 
 /**
  * A factory for {@link UrlRequest}'s, which uses the best HTTP stack
  * available on the current platform.
  */
-public interface UrlRequestFactory {
+public abstract class UrlRequestFactory {
+    private static final String TAG = "UrlRequestFactory";
+    private static final String CRONET_URL_REQUEST_CONTEXT =
+            "org.chromium.net.CronetUrlRequestContext";
+
     /**
      * Creates an UrlRequest object. All UrlRequest functions must
      * be called on the Executor's thread, and all callbacks will be called
@@ -23,4 +31,58 @@ public interface UrlRequestFactory {
      */
     public abstract UrlRequest createRequest(String url,
             UrlRequestListener listener, Executor executor);
+
+    public static UrlRequestFactory createFactory(Context context,

[mmenke, 2014/10/06 18:28:45]

Should have a comment here.

[mmenke, 2014/10/06 18:28:45]

Don't think we really get anything by having two functions here.  My suggestion
is to merge them, particularly since the both have logic to create the wrapper.

i.e.

if (config.legacyMode()) {
  try {
    ...
    if (cronetFactory.isEnabled()) {
      factory = cronetFactory;
    }
  }
  catch...
}
if (!factory) {
  // Try to create wrapper here.
}

Log.i(...);
return factory;

Alternatively, move the legacyMode check and all creation logic into
createCronetFactory.

[mef, 2014/10/07 00:45:18]

Done.

[mef, 2014/10/21 21:27:47]

Done.

+            String userAgent, HttpUrlRequestFactoryConfig config) {
+        UrlRequestFactory factory = null;
+        if (config.userAgent().isEmpty()) {
+            config.setUserAgent(UserAgent.from(context));
+        }
+        if (!config.legacyMode()) {
+            factory = createCronetFactory(context, config);
+        }
+        if (factory == null) {
+            // TODO(mef): Fallback to stub implementation.
+            factory = createCronetFactory(context, config);
+        }
+        Log.i(TAG, "Using network stack: " + factory.getName());
+        return factory;
+    }
+
+    /**
+     * @return true if the factory is enabled.
+     */
+    public abstract boolean isEnabled();
+
+    /**
+     * @return a human-readable name of the factory.
+     */
+    public abstract String getName();
+
+    private static UrlRequestFactory createCronetFactory(Context context,
+            HttpUrlRequestFactoryConfig config) {
+        UrlRequestFactory factory = null;
+        try {
+            Class<? extends UrlRequestFactory> factoryClass =
+                    UrlRequestFactory.class.getClassLoader().
+                            loadClass(CRONET_URL_REQUEST_CONTEXT).
+                            asSubclass(UrlRequestFactory.class);
+            Constructor<? extends UrlRequestFactory> constructor =
+                    factoryClass.getConstructor(
+                            Context.class, HttpUrlRequestFactoryConfig.class);
+            UrlRequestFactory cronetFactory =
+                    constructor.newInstance(context, config);
+            if (cronetFactory.isEnabled()) {
+                factory = cronetFactory;
+            }
+        } catch (ClassNotFoundException e) {
+            // Leave as null

[mmenke, 2014/10/06 18:28:45]

nit:  +.

[mmenke, 2014/10/06 18:28:45]

Should we even have this case for now, or just throw an exception?  Think the
exception means failure can be handled consistently, as opposed to needing a
null check before we've implemented a wrapper around HttpURLConnection, and
catching an exception afterwards.

[mef, 2014/10/21 21:27:47]

Done.

+        } catch (Exception e) {
+            throw new IllegalStateException(
+                    "Cannot instantiate: " +
+                    CRONET_URL_REQUEST_CONTEXT,
+                    e);
+        }
+        return factory;
+    }
 }