Fix polymer tests and a couple bugs

pkg/polymer/test/build/import_inliner_test.dart

Index: pkg/polymer/test/build/import_inliner_test.dart
diff --git a/pkg/polymer/test/build/import_inliner_test.dart b/pkg/polymer/test/build/import_inliner_test.dart
index 6efca44ba96bb338adf8d152467bf2c87fd9e9d0..7db7e4f8767a345fd4eccf0fc9094497fc9ef87d 100644
--- a/pkg/polymer/test/build/import_inliner_test.dart
+++ b/pkg/polymer/test/build/import_inliner_test.dart
@@ -617,7 +617,7 @@ void stylesheetTests() {
           '<link rel="stylesheet" href="assets/b/test3.css">'
           '</polymer-element>',
       'b|asset/test3.css':
-          'body {\n  background: #eaeaea url("assets/b/test4.png");\n}\n'
+          'body {\n  background: #eaeaea url("../../assets/b/test4.png");\n}\n'
           '.foo {\n  background: url("../../packages/c/test5.png");\n}',
       'b|asset/test4.png': 'PNG',
       'c|lib/test5.png': 'PNG',
@@ -641,7 +641,7 @@ void stylesheetTests() {
           '</polymer-element>'
           '</body></html>',
       'b|asset/test3.css':
-          'body {\n  background: #eaeaea url("assets/b/test4.png");\n}\n'
+          'body {\n  background: #eaeaea url("../../assets/b/test4.png");\n}\n'
           '.foo {\n  background: url("../../packages/c/test5.png");\n}',
       'b|asset/test4.png': 'PNG',
       'c|lib/test5.png': 'PNG',