Reland: Start checking URLs using PVer4. Verdict not returned to client yet.

components/safe_browsing_db/v4_local_database_manager.h

Index: components/safe_browsing_db/v4_local_database_manager.h
diff --git a/components/safe_browsing_db/v4_local_database_manager.h b/components/safe_browsing_db/v4_local_database_manager.h
index f9510c4af51fceb49f9b354f6f31c2ab34a57558..c73db1b97164ae41238b5861db9cb214b0ce7bc3 100644
--- a/components/safe_browsing_db/v4_local_database_manager.h
+++ b/components/safe_browsing_db/v4_local_database_manager.h
@@ -28,18 +28,10 @@ typedef unsigned ThreatSeverity;
 // SafeBrowsing service and interfaces with the protocol manager.
 class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
  public:
-  enum class ClientCallbackType {
-    // This represents the case when we're trying to determine if a URL is
-    // unsafe from the following perspectives: Malware, Phishing, UwS.
-    CHECK_BROWSE_URL = 0,
-
-    // This should always be the last value.
-    CHECK_MAX
-  };
-
-  // Construct V4LocalDatabaseManager.
-  // Must be initialized by calling StartOnIOThread() before using.
-  V4LocalDatabaseManager(const base::FilePath& base_path);
+  // Create and return an instance of V4LocalDatabaseManager, if Finch trial
+  // allows it; nullptr otherwise.
+  static scoped_refptr<V4LocalDatabaseManager> Create(
+      const base::FilePath& base_path);
 
   //
   // SafeBrowsingDatabaseManager implementation
@@ -74,6 +66,19 @@ class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
   //
 
  protected:
+  // Construct V4LocalDatabaseManager.
+  // Must be initialized by calling StartOnIOThread() before using.
+  V4LocalDatabaseManager(const base::FilePath& base_path);
+
+  enum class ClientCallbackType {
+    // This represents the case when we're trying to determine if a URL is
+    // unsafe from the following perspectives: Malware, Phishing, UwS.
+    CHECK_BROWSE_URL = 0,
+
+    // This should always be the last value.
+    CHECK_MAX
+  };
+
   // The information we need to process a URL safety reputation request and
   // respond to the SafeBrowsing client that asked for it.
   // TODO(vakh): In its current form, it only includes information for