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 dd7b0819b55e4f5258e5e6789549cbf91a645c0b..781bd6950af127b4409bf32d1259e33117bfe7d7 100644
--- a/build/config/features.gni
+++ b/build/config/features.gni
@@ -133,11 +133,12 @@ use_dbus = is_linux
 
 enable_extensions = !is_android && !is_ios
 
-# 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) {