Produce code coverage only once

This should fix variations in code coverage due to hhvm finishing before
any of the PHP builds. It should also make the tests run faster on Travis.

Author: ddeboer

.travis.yml

@@ -4,7 +4,6 @@ php:
   - 5.3
   - 5.4
   - 5.5
-  - 5.6
   - hhvm
 
 branches:
@@ -32,6 +31,10 @@ matrix:
       env:
         - SYMFONY_VERSION='2.7.*@dev'
         - FRAMEWORK_EXTRA_VERSION='~3.0'
+    - php: 5.6
+      env:
+        - PHPUNIT_FLAGS="--coverage-clover=coverage.clover"
+        - COVERAGE=true
 
 # only needed for the hackaround for https://github.com/symfony/symfony/issues/12868
 before_install:
@@ -47,13 +50,13 @@ before_script:
   - sudo pip install -r Resources/doc/requirements.txt
 
 script:
-  - phpunit --coverage-clover=coverage.clover
+  - phpunit ${PHPUNIT_FLAGS}
   - make -C Resources/doc SPHINXOPTS='-nW' html
   - make -C Resources/doc spelling
 
 after_script:
-  - wget https://scrutinizer-ci.com/ocular.phar
-  - php ocular.phar code-coverage:upload --format=php-clover coverage.clover
+  - if [[ "$COVERAGE" = true ]]; then wget https://scrutinizer-ci.com/ocular.phar; fi
+  - if [[ "$COVERAGE" = true ]]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi
 
 after_failure:
   - cat /tmp/fos-http-cache-bundle/logs/test.log