Clean test reference to deleted object.

This can cause following tests in the same batch to crash.

Bug: 1006412
Change-Id: I6ac3dce5dadc50aee74f5dcfcbef30730dbb422c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1817155Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Ilia Samsonov <isamsonov@google.com>
Cr-Commit-Position: refs/heads/master@{#701847}

chrome/browser/policy/chrome_browser_policy_connector_unittest.cc

@@ -30,6 +30,7 @@ TEST(ChromeBrowserPolicyConnectorTest, HasMachineLevelPolicies) {
           nullptr);
   provider.UpdateChromePolicy(map);
   EXPECT_TRUE(connector.HasMachineLevelPolicies());
+  BrowserPolicyConnectorBase::SetPolicyProviderForTesting(nullptr);
 }
 #endif  // !defined(OS_CHROMEOS)
 

components/policy/core/browser/browser_policy_connector_base.cc

@@ -112,7 +112,6 @@ void BrowserPolicyConnectorBase::SetPolicyProviderForTesting(
   // If this function is used by a test then it must be called before the
   // browser is created, and GetPolicyService() gets called.
   CHECK(!g_created_policy_service);
-  DCHECK(!g_testing_provider);
   g_testing_provider = provider;
 }