Fix flaky test DeepScanningReportingTest.ProcessesResponseCorrectly.

This test tried to use a service whose factory is null in test mode.
It would work if run standalone because the factory was _also_ not
properly registered on startup, so the testing factory would never be
set to null.  However, if run in a batch with other browser tests, a
previous test's access to the factory would register it; the next
browser startup would null its testing factory; and then this test
would crash.

This fixes both problems: registers the factory, and sets a non-null
testing factory.

Bug: none
Change-Id: I877cb9b7c58e82de17888b52d7d6ddc34f5bec27
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2133626Reviewed-by: David Bertoni <dbertoni@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755866}

chrome/browser/extensions/browser_context_keyed_service_factories.cc

@@ -25,6 +25,7 @@
 #include "chrome/browser/extensions/api/passwords_private/passwords_private_event_router_factory.h"
 #include "chrome/browser/extensions/api/preference/preference_api.h"
 #include "chrome/browser/extensions/api/processes/processes_api.h"
+#include "chrome/browser/extensions/api/safe_browsing_private/safe_browsing_private_event_router_factory.h"
 #include "chrome/browser/extensions/api/sessions/sessions_api.h"
 #include "chrome/browser/extensions/api/settings_overrides/settings_overrides_api.h"
 #include "chrome/browser/extensions/api/settings_private/settings_private_event_router_factory.h"
@@ -116,6 +117,7 @@ void EnsureBrowserContextKeyedServiceFactoriesBuilt() {
 #endif
   extensions::PreferenceAPI::GetFactoryInstance();
   extensions::ProcessesAPI::GetFactoryInstance();
+  extensions::SafeBrowsingPrivateEventRouterFactory::GetInstance();
   extensions::SessionsAPI::GetFactoryInstance();
   extensions::SettingsPrivateEventRouterFactory::GetInstance();
   extensions::SettingsOverridesAPI::GetFactoryInstance();

chrome/browser/safe_browsing/download_protection/deep_scanning_request_unittest.cc

@@ -16,6 +16,7 @@
 #include "chrome/browser/safe_browsing/dm_token_utils.h"
 #include "chrome/browser/safe_browsing/download_protection/download_protection_service.h"
 #include "chrome/browser/safe_browsing/download_protection/download_protection_util.h"
+#include "chrome/browser/safe_browsing/test_extension_event_observer.h"
 #include "chrome/test/base/testing_browser_process.h"
 #include "chrome/test/base/testing_profile.h"
 #include "chrome/test/base/testing_profile_manager.h"
@@ -354,11 +355,13 @@ class DeepScanningReportingTest : public DeepScanningRequestTest {
  public:
   void SetUp() override {
     DeepScanningRequestTest::SetUp();
-    SetUpReporting();
-  }
 
-  void SetUpReporting() {
     client_ = std::make_unique<policy::MockCloudPolicyClient>();
+
+    extensions::SafeBrowsingPrivateEventRouterFactory::GetInstance()
+        ->SetTestingFactory(
+            profile_,
+            base::BindRepeating(&BuildSafeBrowsingPrivateEventRouter));
     extensions::SafeBrowsingPrivateEventRouterFactory::GetForProfile(profile_)
         ->SetCloudPolicyClientForTesting(client_.get());
     extensions::SafeBrowsingPrivateEventRouterFactory::GetForProfile(profile_)
@@ -366,6 +369,7 @@ class DeepScanningReportingTest : public DeepScanningRequestTest {
             download_protection_service_.GetFakeBinaryUploadService());
     download_protection_service_.GetFakeBinaryUploadService()
         ->SetAuthForTesting(true);
+
     TestingBrowserProcess::GetGlobal()->local_state()->SetBoolean(
         prefs::kUnsafeEventsReportingEnabled, true);
   }