Revert of Remove support for GlobalNetworkClientFactory from RequestTracker.

ios/net/request_tracker.mm

Index: ios/net/request_tracker.mm
diff --git a/ios/net/request_tracker.mm b/ios/net/request_tracker.mm
index 85dce7ffdf4d4dcc33eabfe457e70581d2b7e733..f72921a3398e92988483bf9f9db81e6f9474b4ca 100644
--- a/ios/net/request_tracker.mm
+++ b/ios/net/request_tracker.mm
@@ -18,6 +18,56 @@
 
 // Reference to the single instance of the RequestTrackerFactory.
 RequestTracker::RequestTrackerFactory* g_request_tracker_factory = nullptr;
+
+// Array of network client factories that should be added to any new request
+// tracker.
+class GlobalNetworkClientFactories {
+ public:
+  static GlobalNetworkClientFactories* GetInstance() {
+    if (!g_global_network_client_factories)
+      g_global_network_client_factories = new GlobalNetworkClientFactories;
+    return g_global_network_client_factories;
+  }
+
+  // Gets the factories.
+  NSArray* GetFactories() {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    return factories_.get();
+  }
+
+  // Adds a factory.
+  void AddFactory(CRNForwardingNetworkClientFactory* factory) {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    DCHECK_EQ(NSNotFound,
+              static_cast<NSInteger>([factories_ indexOfObject:factory]));
+    DCHECK(!IsSelectorOverriden(factory, @selector(clientHandlingRequest:)));
+    DCHECK(!IsSelectorOverriden(factory,
+                                @selector(clientHandlingResponse:request:)));
+    DCHECK(!IsSelectorOverriden(
+               factory, @selector(clientHandlingRedirect:url:response:)));
+    [factories_ addObject:factory];
+  }
+
+  // Returns true if |factory| re-implements |selector|.
+  // Only used for debugging.
+  bool IsSelectorOverriden(CRNForwardingNetworkClientFactory* factory,
+                           SEL selector) {
+    return
+        [factory methodForSelector:selector] !=
+        [CRNForwardingNetworkClientFactory instanceMethodForSelector:selector];
+  }
+
+ private:
+  GlobalNetworkClientFactories() : factories_([[NSMutableArray alloc] init]) {}
+
+  base::scoped_nsobject<NSMutableArray> factories_;
+  base::ThreadChecker thread_checker_;
+
+  static GlobalNetworkClientFactories* g_global_network_client_factories;
+};
+
+GlobalNetworkClientFactories*
+    GlobalNetworkClientFactories::g_global_network_client_factories = nullptr;
 
 }  // namespace
 
@@ -58,6 +108,12 @@
   }
 }
 
+// static
+void RequestTracker::AddGlobalNetworkClientFactory(
+    CRNForwardingNetworkClientFactory* factory) {
+  GlobalNetworkClientFactories::GetInstance()->AddFactory(factory);
+}
+
 RequestTracker::RequestTracker()
     : client_factories_([[NSMutableArray alloc] init]),
       initialized_(false),
@@ -83,6 +139,22 @@
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!initialized_);
   initialized_ = true;
+  for (CRNForwardingNetworkClientFactory* factory in
+           GlobalNetworkClientFactories::GetInstance()->GetFactories()) {
+    AddNetworkClientFactory(factory);
+  }
+}
+
+// static
+NSArray* RequestTracker::GlobalClientsHandlingAnyRequest() {
+  NSMutableArray* applicable_clients = [NSMutableArray array];
+  for (CRNForwardingNetworkClientFactory* factory in
+           GlobalNetworkClientFactories::GetInstance()->GetFactories()) {
+    CRNForwardingNetworkClient* client = [factory clientHandlingAnyRequest];
+    if (client)
+      [applicable_clients addObject:client];
+  }
+  return applicable_clients;
 }
 
 NSArray* RequestTracker::ClientsHandlingAnyRequest() {