add missing methods

src/harness/harnessLanguageService.ts

@@ -646,6 +646,10 @@ namespace Harness.LanguageService {
             return true;
         }
 
+        getLogFileName(): string {
+            return undefined;
+        }
+
         hasLevel() {
             return false;
         }

src/harness/unittests/cachingInServerLSHost.ts

@@ -81,7 +81,8 @@ namespace ts {
             info: (s: string) => { },
             startGroup: () => { },
             endGroup: () => { },
-            msg: (s: string, type?: string) => { }
+            msg: (s: string, type?: string) => { },
+            getLogFileName: (): string => undefined
         };
 
         const projectService = new server.ProjectService(serverHost, logger, { isCancellationRequested: () => false }, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined);

src/harness/unittests/session.ts

@@ -36,6 +36,7 @@ namespace ts.server {
         startGroup(): void {},
         endGroup(): void {},
         msg(s: string, type?: string): void {},
+        getLogFileName: (): string => undefined
     };
 
     describe("the Session class", () => {

src/harness/unittests/tsserverProjectSystem.ts

@@ -14,7 +14,8 @@ namespace ts {
         info: () => void 0,
         startGroup: () => void 0,
         endGroup: () => void 0,
-        msg: () => void 0
+        msg: () => void 0,
+        getLogFileName: (): string => undefined
     };
 
     const nullCancellationToken: HostCancellationToken = {