Fix DownloadProtectionServiceTest when APP scanning is enabled

Enabling this feature flag would cause the DownloadProtectionServiceTest
to look for an AdvancedProtectionStatusManager, which did not exist.
This CL fixes that.

Patch set 3 demonstrates that all tests now pass with the feature flag
enabled.

Change-Id: I90d771b0ca7a297e7f81509019c6f6de09ded3a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410847
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Bettina Dea <bdea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807132}

chrome/browser/safe_browsing/download_protection/check_client_download_request.cc

@@ -330,9 +330,14 @@ bool CheckClientDownloadRequest::ShouldPromptForDeepScanning(
   return false;
 #else
   Profile* profile = Profile::FromBrowserContext(GetBrowserContext());
+  if (!profile)
+    return false;
+  AdvancedProtectionStatusManager* advanced_protection_status_manager =
+      AdvancedProtectionStatusManagerFactory::GetForProfile(profile);
+  if (!advanced_protection_status_manager)
+    return false;
   return base::FeatureList::IsEnabled(kPromptAppForDeepScanning) &&
-         AdvancedProtectionStatusManagerFactory::GetForProfile(profile)
-             ->IsUnderAdvancedProtection();
+         advanced_protection_status_manager->IsUnderAdvancedProtection();
 #endif
 }