Revert of Remove support for GlobalNetworkClientFactory from RequestTracker.

ios/net/request_tracker.h

Index: ios/net/request_tracker.h
diff --git a/ios/net/request_tracker.h b/ios/net/request_tracker.h
index 13c0d11ab32a523e2f27084a852caccb9fbc0ef2..1260b15669e611fcf0850c984077a8a18cf86894 100644
--- a/ios/net/request_tracker.h
+++ b/ios/net/request_tracker.h
@@ -79,6 +79,14 @@
   // this tracker.
   void AddNetworkClientFactory(CRNForwardingNetworkClientFactory* factory);
 
+  // Registers a factory with the class that will be added to all trackers.
+  // Requests without associated trackers can add clients from these factories
+  // using GlobalClientsHandlingAnyRequest().
+  // Only |-clientHandlingAnyRequest| will be called on |factory|, the other
+  // methods are not supported.
+  static void AddGlobalNetworkClientFactory(
+      CRNForwardingNetworkClientFactory* factory);
+
   // Gets the request context associated with the tracker.
   virtual URLRequestContext* GetRequestContext() = 0;
 
@@ -87,6 +95,10 @@
   // to the CRNForwardingNetworkClientFactories added to the tracker. The array
   // may be empty. The caller is responsible for taking ownership of the clients
   // in the array.
+
+  // Static method that returns clients that can handle any request, for use
+  // in cases where a request isn't associated with any request_tracker.
+  static NSArray* GlobalClientsHandlingAnyRequest();
 
   // Returns clients that can handle any request.
   NSArray* ClientsHandlingAnyRequest();