[subresource_filter] Move driver factory tests to the SB throttle

BUG=717590

Review-Url: https://codereview.chromium.org/2887253004
Cr-Commit-Position: refs/heads/master@{#474000}

components/subresource_filter/content/browser/BUILD.gn

@@ -76,7 +76,6 @@ source_set("unit_tests") {
     "activation_state_computing_navigation_throttle_unittest.cc",
     "async_document_subresource_filter_unittest.cc",
     "content_ruleset_service_unittest.cc",
-    "content_subresource_filter_driver_factory_unittest.cc",
     "content_subresource_filter_throttle_manager_unittest.cc",
     "subframe_navigation_filtering_throttle_unittest.cc",
     "subresource_filter_safe_browsing_activation_throttle_unittest.cc",

components/subresource_filter/core/common/activation_decision.h

@@ -8,7 +8,7 @@
 namespace subresource_filter {
 
 // NOTE: ActivationDecision backs a UMA histogram, so it is append-only.
-enum class ActivationDecision {
+enum class ActivationDecision : int {
   // The activation decision is unknown, or not known yet.
   UNKNOWN,