message: Second attempt at conditionally executing tests requiring WebGL context.
  Bill Goehrig claims this will work.
diff: @@ -8,9 +8,9 @@ import { IModelApp } from "@bentley/imodeljs-frontend";
  export namespace WebGLTestContext {
  // When executing on the continuous integration server, we fail to obtain a WebGLRenderingContext.
  // Need to determine why, and how to fix.
  - // For now, all tests requiring WebGL are disabled by default; enable in developer builds by setting
  - // isEnabled to true.
  - const isEnabled = false;
  + // Bill Goehrig claims one or both of these env vars will be defined when executing on the CI server.
  + function isEnabled(): boolean { return undefined === process.env.CI && undefined === process.env.TF_BUILD; }
  +
  const canvasId = "WebGLTestCanvas";
  function createCanvas(width: number, height: number): HTMLCanvasElement | undefined {
  @@ -35,7 +35,7 @@ export namespace WebGLTestContext {
  export let isInitialized = false;
  export function startup(canvasWidth: number = 300, canvasHeight: number = 150) {
  - if (!isEnabled) {
  + if (!isEnabled()) {
  return;
  }
  