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 7fcc0188910926880b3c31bcef31ae249e2d773a..2f3c149312015bb6a7f3fe3eadba7c8e614f7e3d 100644
--- a/content/browser/frame_host/navigation_handle_impl.h
+++ b/content/browser/frame_host/navigation_handle_impl.h
@@ -134,8 +134,14 @@ 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> >;

[davidben, 2015/12/03 23:44:56]

"> >" can be >> now

+  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);

[davidben, 2015/12/03 23:44:57]

This is only to be used by the DRP SafeBrowsing hack, right? Given
https://crbug.com/474608, it might be that that code is short-lived anyway.
Might be worth checking with the status of this and adding a TODO to remove this
API of their plan is to remove the DRP code altogether. ResourceThrottles
changing headers makes me nervous, though that ship seems to have already
sailed.

 
   // Called when the URLRequest will start in the network stack.  |callback|
   // will be called when all throttle checks have completed. This will allow
@@ -238,6 +244,10 @@ class CONTENT_EXPORT NavigationHandleImpl : public NavigationHandle {
   // The time this navigation started.
   const base::TimeTicks navigation_start_;
 
+  // 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_;