Split to SafeBrowsingDatabaseManager into Local* and Remote*.

build/config/features.gni

Index: build/config/features.gni
diff --git a/build/config/features.gni b/build/config/features.gni
index 290c1d6d831f70ad296ea8b6c5c12fe66d13b2ee..0a543fefc1867ec99b9587a31e36439caf532078 100644
--- a/build/config/features.gni
+++ b/build/config/features.gni
@@ -86,12 +86,12 @@ declare_args() {
   # (e.g. Android and ChromeCast) that use a browser side CDM.
   enable_browser_cdms = is_android
 
-  # Variable safe_browsing is used to control the build time configuration for
-  # safe browsing feature. Safe browsing can be compiled in 3 different levels:
-  # 0 disables it, 1 enables it fully, and 2 enables only UI and reporting
-  # features without enabling phishing and malware detection. This is useful to
-  # integrate a third party phishing/malware detection to existing safe browsing
-  # logic.
+  # Variable safe_browsing is used to control the build time configuration
+  # for safe browsing feature. Safe browsing can be compiled in 4 different
+  # levels: 0 disables it, 1 enables it fully, and 2 enables only UI and
+  # reporting features for use with Data Saver on Mobile, and 3 enables
+  # extended mobile protection via an external API.  When 3 is fully deployed,
+  # it will replace 2.
   if (is_android) {
     safe_browsing_mode = 2
   } else if (is_ios) {