Enable (optional) blocking of webrequests in case a PAC script cannot be fetched or is invalid.

net/proxy/proxy_config.h

Index: net/proxy/proxy_config.h
diff --git a/net/proxy/proxy_config.h b/net/proxy/proxy_config.h
index 9012a316652ef3f1b2161d398dacc1b45c551a80..dc0fd71d2f966e5811f7f73a113344f39c7a0595 100644
--- a/net/proxy/proxy_config.h
+++ b/net/proxy/proxy_config.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -148,6 +148,14 @@ class ProxyConfig {
     return pac_url_;
   }
 
+  void set_pac_mandatory(bool enable_pac_mandatory) {
+    pac_mandatory_ = enable_pac_mandatory;
+  }
+
+  bool pac_mandatory() const {
+    return pac_mandatory_;
+  }
+
   bool has_pac_url() const {
     return pac_url_.is_valid();
   }
@@ -175,6 +183,8 @@ class ProxyConfig {
   static ProxyConfig CreateFromCustomPacURL(const GURL& pac_url) {
     ProxyConfig config;
     config.set_pac_url(pac_url);
+    // By default fall back to direct connection in case PAC script fails.
+    config.set_pac_mandatory(false);
     return config;
   }
 
@@ -185,6 +195,10 @@ class ProxyConfig {
   // If non-empty, indicates the URL of the proxy auto-config file to use.
   GURL pac_url_;
 
+  // If true, blocks all traffic in case fetching the pac script from |pac_url_|
+  // fails. Only valid if |pac_url_| is non-empty.
+  bool pac_mandatory_;
+
   // Manual proxy settings.
   ProxyRules proxy_rules_;