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

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

Index: components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
diff --git a/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java b/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
index 4c7afc6c0f2278fc2be06da86220681d7d2ee5ac..5846ecebc29c64cd0627d3452d34cf601b263560 100644
--- a/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
+++ b/components/cronet/android/java/src/org/chromium/net/CronetUrlRequestContext.java
@@ -6,6 +6,8 @@ package org.chromium.net;
 
 import android.content.Context;
 import android.os.Build;
+import android.os.Handler;
+import android.os.Looper;
 import android.os.Process;
 import android.util.Log;
 
@@ -31,12 +33,25 @@ public class CronetUrlRequestContext extends UrlRequestContext  {
 
     public CronetUrlRequestContext(Context context,
                                    UrlRequestContextConfig config) {
+        CronetLibraryLoader.ensureInitialized(context, config);
         nativeSetMinLogLevel(getLoggingLevel());
+        final String configString = config.toString();
         mUrlRequestContextAdapter = nativeCreateRequestContextAdapter(
-                context, config.toString());
+                context, configString);
         if (mUrlRequestContextAdapter == 0) {
             throw new NullPointerException("Context Adapter creation failed");
         }
+        // Post a task to UI thread to init native Chromium URLRequestContext.
+        // TODO(xunjieli): This constructor is not supposed to be invoked on
+        // the main thread. Consider making the following code into a blocking
+        // API to handle the case where we are already on main thread.
+        Runnable task = new Runnable() {
+            public void run() {
+                nativeInitRequestContextOnMainThread(
+                        mUrlRequestContextAdapter, configString);
+            }
+        };
+        new Handler(Looper.getMainLooper()).post(task);
     }
 
     @Override
@@ -146,4 +161,7 @@ public class CronetUrlRequestContext extends UrlRequestContext  {
     private native void nativeStopNetLog(long urlRequestContextAdapter);
 
     private native int nativeSetMinLogLevel(int loggingLevel);
+
+    private native void nativeInitRequestContextOnMainThread(
+            long urlRequestContextAdapter, String config);
 }