Add HasInstance method to TestNetworkConnectionTracker

Currently GetInstance() has a DCHECK for the instance pointer and
CreateInstance() overrides the current pointer, so there is no
way to check if CreateInstance() was already called.

We need to get a pointer to TestNetworkConnectionTracker in
IdentityTestEnvironment. Since some tests create it (e.g. if they use
TestingBrowserProcess) and others don't, we need a way to know if
CreateInstance was called.

Bug: 1068240
Change-Id: I99bb1dc64a170203beaae71d76de73d0b4483af9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307249
Commit-Queue: Anastasiia N <anastasiian@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792351}

services/network/test/test_network_connection_tracker.cc

@@ -15,7 +15,8 @@
 
 namespace network {
 
-static TestNetworkConnectionTracker* g_test_network_connection_tracker_instance;
+static TestNetworkConnectionTracker*
+    g_test_network_connection_tracker_instance = nullptr;
 
 namespace {
 
@@ -50,6 +51,11 @@ TestNetworkConnectionTracker* TestNetworkConnectionTracker::GetInstance() {
   return g_test_network_connection_tracker_instance;
 }
 
+// static
+bool TestNetworkConnectionTracker::HasInstance() {
+  return g_test_network_connection_tracker_instance != nullptr;
+}
+
 // static
 NetworkConnectionTrackerGetter TestNetworkConnectionTracker::CreateGetter() {
   return base::BindRepeating(&GetNonTestInstance);

services/network/test/test_network_connection_tracker.h

@@ -25,6 +25,10 @@ class TestNetworkConnectionTracker : public NetworkConnectionTracker {
   // CreateInstance() must have been called before calling this.
   static TestNetworkConnectionTracker* GetInstance();
 
+  // Returns true if TestNetworkConnectionTracker instance already exists.
+  // It means that CreateInstance() was already called.
+  static bool HasInstance();
+
   // Creates a NetworkConnectionTrackerGetter that will return the active
   // TestNetworkConnectionTracker instance when called.
   static NetworkConnectionTrackerGetter CreateGetter();