fix: coverage issue with saucelabs (#3540)

* Saucelabs seems to have issues with Edge and the `karma-coverage` plugin.

* Running on Browserstack seems to be work without any flakiness and also makes the build faster (runs less browsers than on saucelabs)

scripts/ci/build-and-test.sh

@@ -25,8 +25,8 @@ else
   $(npm bin)/gulp ci:test
 fi
 
-# Don't upload coverage for both test modes (browserstack and saucelabs) and inside of PRs.
-if [[ "$MODE" == "saucelabs_required" ]] && [ "$TRAVIS_PULL_REQUEST" = "false" ]; then
+# Upload coverage results if those are present.
+if [ -f dist/coverage/coverage-summary.json ]; then
   $(npm bin)/gulp ci:coverage
 fi
 

test/karma.conf.js

@@ -106,7 +106,9 @@ module.exports = (config) => {
   if (process.env['TRAVIS']) {
     let buildId = `TRAVIS #${process.env.TRAVIS_BUILD_NUMBER} (${process.env.TRAVIS_BUILD_ID})`;
 
-    if (process.env['TRAVIS_PULL_REQUEST'] === 'false') {
+    if (process.env['TRAVIS_PULL_REQUEST'] === 'false' &&
+        process.env['MODE'] === "browserstack_required") {
+
       config.preprocessors['dist/@angular/material/**/!(*+(.|-)spec).js'] = ['coverage'];
       config.reporters.push('coverage');
     }