[Cronet] Hook up library loader, system proxy and network change notifier to async api.

components/cronet/android/cronet_url_request_context.cc

Index: components/cronet/android/cronet_url_request_context.cc
diff --git a/components/cronet/android/cronet_url_request_context.cc b/components/cronet/android/cronet_url_request_context.cc
index a9b6014217c7ffd110f42fa9a90a4eea5a3227da..b4592fc1d42ddb2acadc6512c9a9b44ff9a507e0 100644
--- a/components/cronet/android/cronet_url_request_context.cc
+++ b/components/cronet/android/cronet_url_request_context.cc
@@ -106,4 +106,16 @@ static jint SetMinLogLevel(JNIEnv* env, jobject jcaller, jint jlog_level) {
   return old_log_level;
 }
 
+// Called on application's main Java thread.
+static void InitRequestContextOnMainThread(JNIEnv* env,
+                                           jobject jcaller,
+                                           jlong jurl_request_context_adapter) {
+  if (jurl_request_context_adapter == 0)
+    return;
+  CronetURLRequestContextAdapter* context_adapter =
+      reinterpret_cast<CronetURLRequestContextAdapter*>(
+          jurl_request_context_adapter);
+  context_adapter->InitRequestContextOnMainThread();
+}
+
 }  // namespace cronet