Enable using system proxy resolver for android webview.

net/proxy/proxy_config_service_android.cc

Index: net/proxy/proxy_config_service_android.cc
diff --git a/net/proxy/proxy_config_service_android.cc b/net/proxy/proxy_config_service_android.cc
index f1a0b6cca54f702b924b969ba320d691b61b1108..50407fe21b7b44dd923730b2f948ab1e0b84efc8 100644
--- a/net/proxy/proxy_config_service_android.cc
+++ b/net/proxy/proxy_config_service_android.cc
@@ -197,7 +197,8 @@ class ProxyConfigServiceAndroid::Delegate
       : jni_delegate_(this),
         network_task_runner_(network_task_runner),
         jni_task_runner_(jni_task_runner),
-        get_property_callback_(get_property_callback) {
+        get_property_callback_(get_property_callback),
+        exclude_pac_url_(false) {
   }
 
   void SetupJNI() {
@@ -271,13 +272,22 @@ class ProxyConfigServiceAndroid::Delegate
                               const std::vector<std::string>& exclusion_list) {
     DCHECK(OnJNIThread());
     ProxyConfig proxy_config;
-    CreateStaticProxyConfig(host, port, pac_url, exclusion_list, &proxy_config);
+    if (exclude_pac_url_) {
+      CreateStaticProxyConfig(host, port, "", exclusion_list, &proxy_config);
+    } else {
+      CreateStaticProxyConfig(host, port, pac_url, exclusion_list,
+          &proxy_config);
+    }
     network_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(
             &Delegate::SetNewConfigOnNetworkThread, this, proxy_config));
   }
 
+  void set_exclude_pac_url(bool enabled) {
+    exclude_pac_url_ = enabled;
+  }
+
  private:
   friend class base::RefCountedThreadSafe<Delegate>;
 
@@ -344,6 +354,7 @@ class ProxyConfigServiceAndroid::Delegate
   scoped_refptr<base::SequencedTaskRunner> jni_task_runner_;
   GetPropertyCallback get_property_callback_;
   ProxyConfig proxy_config_;
+  bool exclude_pac_url_;
 
   DISALLOW_COPY_AND_ASSIGN(Delegate);
 };
@@ -366,6 +377,10 @@ bool ProxyConfigServiceAndroid::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
+void ProxyConfigServiceAndroid::set_exclude_pac_url(bool enabled) {
+  delegate_->set_exclude_pac_url(enabled);
+}
+
 void ProxyConfigServiceAndroid::AddObserver(Observer* observer) {
   delegate_->AddObserver(observer);
 }