Keep track of network error in ProxyRetryInfo.

net/base/network_delegate.h

Index: net/base/network_delegate.h
diff --git a/net/base/network_delegate.h b/net/base/network_delegate.h
index 2a0c9f0a172cbef91e896c4d72c5e94ac9d6e416..51627c0a5873b48f12e34e5364f5374b22e9e065 100644
--- a/net/base/network_delegate.h
+++ b/net/base/network_delegate.h
@@ -68,8 +68,7 @@ class NET_EXPORT NetworkDelegate : public base::NonThreadSafe {
                           const ProxyService& proxy_service,
                           ProxyInfo* result);
   void NotifyProxyFallback(const ProxyServer& bad_proxy,
-                           int net_error,
-                           bool did_fallback);
+                           int net_error);
   int NotifyBeforeSendHeaders(URLRequest* request,
                               const CompletionCallback& callback,
                               HttpRequestHeaders* headers);
@@ -138,12 +137,12 @@ class NET_EXPORT NetworkDelegate : public base::NonThreadSafe {
                               const ProxyService& proxy_service,
                               ProxyInfo* result);
 
-  // Called when use of |bad_proxy| fails due to |net_error|. |did_fallback| is
-  // true if the proxy service was able to fallback to another proxy
-  // configuration.
+  // Called when use of |bad_proxy| fails due to |net_error|. |net_error| is
+  // the network error encountered, if any, and OK if the fallback was
+  // for a reason other than network error (eg. a component wants to add the
+  // proxy to the retry list so that it is not used).

[Ryan Sleevi, 2014/08/15 18:02:36]

Great, the overall comments have helped better understand how/when this is used
(which is a point of comments :D)

I think the e.g. can be simplified now

"and OK if the fallback was for a reason other than a network error (e.g. the
proxy service was explicitly directed to skip a proxy)"

[Not at Google. Contact bengr, 2014/08/15 19:56:53]

Done.

   virtual void OnProxyFallback(const ProxyServer& bad_proxy,
-                               int net_error,
-                               bool did_fallback);
+                               int net_error);
 
   // Called right before the HTTP headers are sent. Allows the delegate to
   // read/write |headers| before they get sent out. |callback| and |headers| are