Add a function to add extra headers from NavigationThrottle

content/browser/frame_host/navigation_handle_impl.h

Index: content/browser/frame_host/navigation_handle_impl.h
diff --git a/content/browser/frame_host/navigation_handle_impl.h b/content/browser/frame_host/navigation_handle_impl.h
index a72e774e78dad5b6e13a1258daa021a19e521e27..6ecb84f3c4af9545e08cbe0dbdcd2023e2ac75f7 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -112,8 +112,14 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
     return service_worker_handle_.get();
   }
 
-  typedef base::Callback<void(NavigationThrottle::ThrottleCheckResult)>
-      ThrottleChecksFinishedCallback;
+  using ExtraHeadersList = std::vector<std::pair<std::string, std::string> >;

[nasko, 2015/11/25 14:54:37]

nit: I think it is safe these days to have ">>" at the end without need for a
space. 

+  using ThrottleChecksFinishedCallback =
+      base::Callback<void(NavigationThrottle::ThrottleCheckResult,
+                          const ExtraHeadersList&)>;
+
+  // Adds an entry in the ExtraHeadersList. The extra header itself will be
+  // added to the request when the ThrottleChecksFinishedCallback will be run.
+  void AddExtraHeader(const std::string& name, const std::string& value);
 
   // Called when the URLRequest will start in the network stack.  |callback|
   // will be called when all throttle checks have completed. This will allow
@@ -204,6 +210,10 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
   // The index of the next throttle to check.
   size_t next_index_;
 
+  // Passed back to the handler of the navigation request after the throttles
+  // checks have been performed.
+  ExtraHeadersList extra_headers_to_add_;
+
   // This callback will be run when all throttle checks have been performed.
   ThrottleChecksFinishedCallback complete_callback_;