Make "newapi" readonly.

Author: ericsnowcurrently

src/client/common/platform/fileSystem.ts

@@ -66,7 +66,7 @@ interface IRawFSExtra {
 
 export class RawFileSystem implements IRawFileSystem {
     constructor(
-        private newapi: INewAPI = vscode.workspace.fs,
+        private readonly newapi: INewAPI = vscode.workspace.fs,
         private readonly nodefs: IRawFS = fs,
         private readonly fsExtra: IRawFSExtra = fsextra
     ) { }