Add header pointer to BeforeProxyHeadersSentCallback

net/http/http_transaction.h

Index: net/http/http_transaction.h
diff --git a/net/http/http_transaction.h b/net/http/http_transaction.h
index db8ed5211b0d6c1c1c64aa178d7cff02edba0698..52b3c977bde166ab77db767c1c57780a5ed474af 100644
--- a/net/http/http_transaction.h
+++ b/net/http/http_transaction.h
@@ -36,9 +36,11 @@ class NET_EXPORT_PRIVATE HttpTransaction {
 
   // Provides an opportunity to add proxy-specific request headers. Called after
   // it is determined that a proxy is being used and before the request headers
-  // are sent. |proxy_info| contains information about the proxy being used.
+  // are sent. |proxy_info| contains information about the proxy being used,
+  // and additional headers may be added to |request_headers|.
   typedef base::Callback<void(
-      const ProxyInfo& proxy_info)> BeforeProxyHeadersSentCallback;
+      const ProxyInfo& proxy_info,
+      HttpRequestHeaders* request_headers)> BeforeProxyHeadersSentCallback;
 
   // Stops any pending IO and destroys the transaction object.
   virtual ~HttpTransaction() {}