chore: properly exit karma runner (#2653)

* Properly exit karma in single-run mode when errors are recognized.
* This looks like its caused by the karma launchers, that connect to Browserstack or Saucelabs and which doesn't close the connection poperly when karma exits with an error code.

.travis.yml

@@ -4,13 +4,6 @@ sudo: false
 node_js:
   - '6.9.1'
 
-addons:
-  apt:
-    sources:
-      - ubuntu-toolchain-r-test
-    packages:
-      - libstdc++6
-
 branches:
   only:
   - master
@@ -22,11 +15,8 @@ env:
   - SAUCE_ACCESS_KEY=9b988f434ff8-fbca-8aa4-4ae3-35442987
   - BROWSER_STACK_USERNAME=angularteam1
   - BROWSER_STACK_ACCESS_KEY=BWCd4SynLzdDcv8xtzsB
-  - ARCH=linux-x64
   - BROWSER_PROVIDER_READY_FILE=/tmp/angular-material2-build/readyfile
   - BROWSER_PROVIDER_ERROR_FILE=/tmp/angular-material2-build/errorfile
-  # GITHUB_TOKEN_ANGULAR
-  - secure: "fq/U7VDMWO8O8SnAQkdbkoSe2X92PVqg4d044HmRYVmcf6YbO48+xeGJ8yOk0pCBwl3ISO4Q2ot0x546kxfiYBuHkZetlngZxZCtQiFT9kyId8ZKcYdXaIW9OVdw3Gh3tQyUwDucfkVhqcs52D6NZjyE2aWZ4/d1V4kWRO/LMgo="
   matrix:
     # Order: a slower build first, so that we don't occupy an idle travis worker waiting for others to complete.
     - MODE=lint

tools/gulp/tasks/unit-test.ts

@@ -46,7 +46,11 @@ gulp.task('test:single-run', [':test:deps:inline'], (done: () => void) => {
   new karma.Server({
     configFile: path.join(PROJECT_ROOT, 'test/karma.conf.js'),
     singleRun: true
-  }, done).start();
+  }, (exitCode: number) => {
+    // Immediately exit the process if Karma reported errors, because due to
+    // potential still running tunnel-browsers gulp won't exit properly.
+    exitCode === 0 ? done() : process.exit(exitCode);
+  }).start();
 });
 
 /**