Minor tweak to the pubspec.lock output to remove the leading whitespace from the file.

utils/pub/lock_file.dart

Index: utils/pub/lock_file.dart
===================================================================
--- utils/pub/lock_file.dart	(revision 20623)
+++ utils/pub/lock_file.dart	(working copy)
@@ -97,9 +97,10 @@
 
     // TODO(nweiz): Serialize using the YAML library once it supports
     // serialization. For now, we use JSON, since it's a subset of YAML anyway.
-    return '''
-        # Generated by pub. See: http://pub.dartlang.org/doc/glossary.html#lockfile
-         ${json.stringify({'packages': packagesObj})}
-        ''';
+    return
+        '# Generated by pub\n'
+        '# See http://pub.dartlang.org/doc/glossary.html#lockfile\n'
+        '\n'
+        '${json.stringify({'packages': packagesObj})}\n';
   }
 }