systrace: check for errors when compiling JS

Change-Id: I0daba4b5977734ce819451dd9200317d7e0c4ca9
diff --git a/update.py b/update.py
index 357e1a0..37f41c5 100755
--- a/update.py
+++ b/update.py
@@ -1,6 +1,6 @@
-#!/usr/bin/python
+#!/usr/bin/python2.6
 
-import httplib, urllib, subprocess, sys, config
+import config, httplib, json, urllib, subprocess, sys
 
 # Read all the Javascript files.
 js_code = [('js_code', open(f).read()) for f in config.js_in_files]
@@ -13,7 +13,8 @@
 params = urllib.urlencode(js_code + [
   ('language', 'ECMASCRIPT5'),
   ('compilation_level', 'SIMPLE_OPTIMIZATIONS'),
-  ('output_format', 'text'),
+  ('output_format', 'json'),
+  ('output_info', 'errors'),
   ('output_info', 'compiled_code'),
 ])
 
@@ -29,8 +30,20 @@
   print sys.stderr, "error returned from JS compile service: %d" % response.status
   sys.exit(1)
 
-open(config.js_out_file, 'wt').write(data)
-print 'Generated %s.  Check the file to see if errors occured!' % config.js_out_file
+result = json.loads(data)
+if 'errors' in result:
+  for e in result['errors']:
+    filenum = int(e['file'][6:])
+    filename = js_in_files[filenum]
+    lineno = e['lineno']
+    charno = e['charno']
+    err = e['error']
+    print '%s:%d:%d: %s' % (filename, lineno, charno, err)
+  print 'Failed to generate %s.' % config.js_out_file
+  sys.exit(1)
+
+open(config.js_out_file, 'wt').write(result['compiledCode'] + '\n')
+print 'Generated %s' % config.js_out_file
 
 yuic_args = ['yui-compressor', '--type', 'css', '-o', config.css_out_file]
 p = subprocess.Popen(yuic_args, stdin=subprocess.PIPE)
@@ -39,4 +52,4 @@
   print 'Failed to generate %s.' % config.css_out_file
   sys.exit(1)
 
-print 'Generated %s.' % config.css_out_file
+print 'Generated %s' % config.css_out_file