closure: use specific version

using latest may break our tests as minified result may differ

.travis.yml

@@ -8,6 +8,9 @@ php:
   - 5.4
   - hhvm
 
+env:
+  - CLOSURE_VERSION: 20160822
+
 matrix:
   allow_failures:
     - php: hhvm
@@ -25,10 +28,7 @@ install:
   - composer update --no-interaction --prefer-source
 
 before_script:
-  - wget -c https://dl.google.com/closure-compiler/compiler-latest.zip -O vendor/compiler-latest.zip
-  - unzip -od vendor/closure-compiler vendor/compiler-latest.zip
-  - ln -sfn ../$(echo vendor/closure-compiler/closure-compiler-*.jar) tests/compiler.jar
-  - java -jar tests/compiler.jar --version
+  - tests/dl-closure.sh
 
 script:
   - composer validate

tests/dl-closure.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+set -xe
+
+: ${CLOSURE_VERSION:=20160822}
+
+wget -c https://dl.google.com/closure-compiler/compiler-$CLOSURE_VERSION.zip -O vendor/compiler-$CLOSURE_VERSION.zip
+unzip -od vendor/closure-compiler vendor/compiler-$CLOSURE_VERSION.zip
+ln -sfn ../vendor/closure-compiler/closure-compiler-v$CLOSURE_VERSION.jar tests/compiler.jar
+
+# test that version matches
+out=$(java -jar tests/compiler.jar --version)
+
+version=$(echo "$out" | awk '/Version:/{print $NF}')
+version=${version#v}
+
+test "$version" = "$CLOSURE_VERSION"