Set input language for Closure Compiler to ECMAScript 5

Some of the third-party files use constructs not valid in ECMAScript 3 (the
default).

(imported from commit 9292bf23a4860353944c18a6f413b4828cc63e11)

zephyr/lib/minify.py

@@ -26,6 +26,6 @@ class ClosureSourceMapCompressor(SubProcessCompressor):
         source_map = path.join(
             settings.PIPELINE_CLOSURE_SOURCE_MAP_DIR, source_map_name)
 
-        command = '%s --create_source_map %s' % (
+        command = '%s --language_in ECMASCRIPT5 --create_source_map %s' % (
             settings.PIPELINE_CLOSURE_BINARY, source_map)
         return self.execute_command(command, js)