chore(travis): enable both SauceLabs and BrowserStack

Setting env var `BROWSER_PROVIDER` to `browserstack` or `saucelabs`
determines which browser provider will be used.

This does not affect the build as all jobs are set to use SauceLabs.

Switch to Karma with Socket.io 1.x, which solves some issues(*) with BS.
Thus removing `config.transports` as it is not used anymore
(Socket.io 1.x starts with polling and tries to upgrade if available).

(*) folks from BS were fiddling with socket.io configuration to get it stable.
See 4c04011850
This is not necessary with Socket.io 1.x.

scripts/travis/build.sh

@@ -2,13 +2,20 @@
 
 set -e
 
+export BROWSER_STACK_ACCESS_KEY=`echo $BROWSER_STACK_ACCESS_KEY | rev`
 export SAUCE_ACCESS_KEY=`echo $SAUCE_ACCESS_KEY | rev`
 
 if [ $JOB = "unit" ]; then
+  if [ "$BROWSER_PROVIDER" == "browserstack" ]; then
+    BROWSERS="BS_Chrome,BS_Safari,BS_Firefox,BS_IE_9,BS_IE_10,BS_IE_11"
+  else
+    BROWSERS="SL_Chrome,SL_Safari,SL_Firefox,SL_IE_9,SL_IE_10,SL_IE_11"
+  fi
+
   grunt test:promises-aplus
-  grunt test:unit --browsers SL_Chrome,SL_Safari,SL_Firefox,SL_IE_9,SL_IE_10,SL_IE_11 --reporters dots
+  grunt test:unit --browsers $BROWSERS --reporters dots
   grunt ci-checks
-  grunt tests:docs --browsers SL_Chrome,SL_Safari,SL_Firefox,SL_IE_9,SL_IE_10,SL_IE_11 --reporters dots
+  grunt tests:docs --browsers $BROWSERS --reporters dots
   grunt test:travis-protractor --specs "docs/app/e2e/**/*.scenario.js"
 elif [ $JOB = "e2e" ]; then
   if [ $TEST_TARGET = "jquery" ]; then

scripts/travis/start_browser_provider.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# Has to be run from project root directory.
+
+# TODO(vojta): normalize paths to lib/$BROWSER_PROVIDER
+if [ "$BROWSER_PROVIDER" == "browserstack" ]; then
+  echo "Using BrowserStack"
+  ./lib/browser-stack/start-tunnel.sh
+else
+  echo "Using SauceLabs"
+  ./lib/sauce/sauce_connect_setup.sh
+fi