refactor: allow compilation with TypeScript 2.5 (#19966)

A small number of types need to be adjusted. The changes seem to be
backwards compatible with TS 2.4.

PR Close #19966

packages/benchpress/src/runner.ts

@@ -81,7 +81,9 @@ export class Runner {
             {provide: WebDriverAdapter, useValue: adapter}
           ]);
 
-          const sampler = injector.get(Sampler);
+          // TODO: With TypeScript 2.5 injector.get does not infer correctly the
+          // return type. Remove 'any' and investigate the issue.
+          const sampler = injector.get(Sampler) as any;
           return sampler.sample();
         });
   }