dart2js: remove trailing 0 byte when reading .packages

pkg/compiler/lib/src/apiimpl.dart

Index: pkg/compiler/lib/src/apiimpl.dart
diff --git a/pkg/compiler/lib/src/apiimpl.dart b/pkg/compiler/lib/src/apiimpl.dart
index f8695bba1a20c7753c52781d8779c343dd1e4c7a..a2c7d8c9a957ded550c1991ec264f4199629e78d 100644
--- a/pkg/compiler/lib/src/apiimpl.dart
+++ b/pkg/compiler/lib/src/apiimpl.dart
@@ -392,6 +392,13 @@ class Compiler extends leg.Compiler {
         if (packageConfigContents is String) {
           packageConfigContents = UTF8.encode(packageConfigContents);
         }
+        // The input provider may put a trailing 0 byte when it reads a source
+        // file, which confuses the package config parser.
+        if (packageConfigContents.length > 0
+            && packageConfigContents.last == 0) {
+          packageConfigContents = packageConfigContents.sublist(
+              0, packageConfigContents.length - 1);
+        }
         packages =
             new MapPackages(pkgs.parse(packageConfigContents, packageConfig));
       });