--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5108,16 +5108,23 @@ pref("browser.safebrowsing.debug", false
 
 // The protocol version we communicate with google server.
 pref("browser.safebrowsing.provider.google.pver", "2.2");
 pref("browser.safebrowsing.provider.google.lists", "goog-badbinurl-shavar,goog-downloadwhite-digest256,goog-phish-shavar,goog-malware-shavar,goog-unwanted-shavar");
 pref("browser.safebrowsing.provider.google.updateURL", "https://safebrowsing.google.com/safebrowsing/downloads?client=SAFEBROWSING_ID&appver=%MAJOR_VERSION%&pver=2.2&key=%GOOGLE_API_KEY%");
 pref("browser.safebrowsing.provider.google.gethashURL", "https://safebrowsing.google.com/safebrowsing/gethash?client=SAFEBROWSING_ID&appver=%MAJOR_VERSION%&pver=2.2");
 pref("browser.safebrowsing.provider.google.reportURL", "https://safebrowsing.google.com/safebrowsing/diagnostic?client=%NAME%&hl=%LOCALE%&site=");
 
+// Prefs for v4.
+pref("browser.safebrowsing.provider.google4.pver", "4");
+pref("browser.safebrowsing.provider.google4.lists", "goog-phish-proto,goog-malware-proto,goog-unwanted-proto");
+pref("browser.safebrowsing.provider.google4.updateURL", "https://safebrowsing.googleapis.com/v4/threatListUpdates:fetch?$req=%REQUEST_BASE64%&$ct=application/x-protobuf&key=%GOOGLE_API_KEY%");
+pref("browser.safebrowsing.provider.google4.gethashURL", "https://safebrowsing.googleapis.com/v4/fullHashes:find?$req=%REQUEST_BASE64%&$ct=application/x-protobuf&key=%GOOGLE_API_KEY%");
+pref("browser.safebrowsing.provider.google4.reportURL", "https://safebrowsing.google.com/safebrowsing/diagnostic?client=%NAME%&hl=%LOCALE%&site=");
+
 pref("browser.safebrowsing.reportPhishMistakeURL", "https://%LOCALE%.phish-error.mozilla.com/?hl=%LOCALE%&url=");
 pref("browser.safebrowsing.reportPhishURL", "https://%LOCALE%.phish-report.mozilla.com/?hl=%LOCALE%&url=");
 pref("browser.safebrowsing.reportMalwareMistakeURL", "https://%LOCALE%.malware-error.mozilla.com/?hl=%LOCALE%&url=");
 
 // The table and global pref for blocking plugin content
 pref("browser.safebrowsing.blockedURIs.enabled", false);
 pref("urlclassifier.blockedTable", "test-block-simple,mozplugin-block-digest256");
 

--- a/toolkit/components/url-classifier/content/listmanager.js
+++ b/toolkit/components/url-classifier/content/listmanager.js
@@ -348,45 +348,63 @@ PROT_ListManager.prototype.makeUpdateReq
     return;
   }
   // An object of the form
   // { tableList: comma-separated list of tables to request,
   //   tableNames: map of tables that need updating,
   //   request: list of tables and existing chunk ranges from tableData
   // }
   var streamerMap = { tableList: null, tableNames: {}, request: "" };
+  let useProtobuf = false;
   for (var tableName in this.tablesData) {
     // Skip tables not matching this update url
     if (this.tablesData[tableName].updateUrl != updateUrl) {
       continue;
     }
+
+    // Check if |updateURL| is for 'proto'. (only v4 uses protobuf for now.)
+    // We use the table name 'goog-*-proto' and an additional provider "google4"
+    // to describe the v4 settings.
+    let isCurTableProto = tableName.endsWith('-proto');
+    if (useProtobuf && !isCurTableProto) {
+      log('ERROR: Tables for the same updateURL should all be "proto" or none. ' +
+          'Check "browser.safebrowsing.provider.google4.lists"');
+    }
+    useProtobuf = isCurTableProto;
+
     if (this.needsUpdate_[this.tablesData[tableName].updateUrl][tableName]) {
       streamerMap.tableNames[tableName] = true;
     }
     if (!streamerMap.tableList) {
       streamerMap.tableList = tableName;
     } else {
       streamerMap.tableList += "," + tableName;
     }
   }
-  // Build the request. For each table already in the database, include the
-  // chunk data from the database
-  var lines = tableData.split("\n");
-  for (var i = 0; i < lines.length; i++) {
-    var fields = lines[i].split(";");
-    var name = fields[0];
-    if (streamerMap.tableNames[name]) {
-      streamerMap.request += lines[i] + "\n";
-      delete streamerMap.tableNames[name];
+
+  if (useProtobuf) {
+    // TODO: Bug 1275507 - XPCOM API to build v4 update request.
+    streamerMap.request = "";
+  } else {
+    // Build the request. For each table already in the database, include the
+    // chunk data from the database
+    var lines = tableData.split("\n");
+    for (var i = 0; i < lines.length; i++) {
+      var fields = lines[i].split(";");
+      var name = fields[0];
+      if (streamerMap.tableNames[name]) {
+        streamerMap.request += lines[i] + "\n";
+        delete streamerMap.tableNames[name];
+      }
     }
-  }
-  // For each requested table that didn't have chunk data in the database,
-  // request it fresh
-  for (let tableName in streamerMap.tableNames) {
-    streamerMap.request += tableName + ";\n";
+    // For each requested table that didn't have chunk data in the database,
+    // request it fresh
+    for (let tableName in streamerMap.tableNames) {
+      streamerMap.request += tableName + ";\n";
+    }
   }
 
   log("update request: " + JSON.stringify(streamerMap, undefined, 2) + "\n");
 
   // Don't send an empty request.
   if (streamerMap.request.length > 0) {
     this.makeUpdateRequestForEntry_(updateUrl, streamerMap.tableList,
                                     streamerMap.request);