Begin to enable extension APIs in Extension Service Worker.

extensions/common/extensions_client.cc

Index: extensions/common/extensions_client.cc
diff --git a/extensions/common/extensions_client.cc b/extensions/common/extensions_client.cc
index 9f453ef02248fa4d0b026df5a853b75e668b8c64..ec6d686845bd32d22a10816ee66efdfeefcf3d4b 100644
--- a/extensions/common/extensions_client.cc
+++ b/extensions/common/extensions_client.cc
@@ -28,6 +28,10 @@ std::set<base::FilePath> ExtensionsClient::GetBrowserImagePaths(
   return paths;
 }
 
+bool ExtensionsClient::ExtensionAPIEnabledInExtensionServiceWorkers() const {
+  return false;
+}
+
 void ExtensionsClient::Set(ExtensionsClient* client) {
   // This can happen in unit tests, where the utility thread runs in-process.
   if (g_client)