fix(interpolate): escape double quotes, etc. in non-mustache text

Closes #951

Author: chirayuk

lib/core/interpolate.dart

@@ -49,7 +49,7 @@ class Interpolate implements Function {
         if (index < startIdx) {
           // Empty strings could be stripped thanks to the stringify
           // formatter
-          expParts.add('"${template.substring(index, startIdx)}"');
+          expParts.add(JSON.encode(template.substring(index, startIdx)));
         }
         expParts.add('(' + template.substring(startIdx + startLen, endIdx) +
         '|stringify)');
@@ -58,7 +58,7 @@ class Interpolate implements Function {
         hasInterpolation = true;
       } else {
         // we did not find any interpolation, so add the remainder
-        expParts.add('"${template.substring(index)}"');
+        expParts.add(JSON.encode(template.substring(index)));
         break;
       }
     }

lib/core/module_internal.dart

@@ -2,6 +2,7 @@ library angular.core_internal;
 
 import 'dart:async' as async;
 import 'dart:collection';
+import 'dart:convert';
 import 'dart:math';
 import 'package:intl/intl.dart';
 

test/core/interpolate_spec.dart

@@ -33,5 +33,11 @@ main() {
       .toEqual('"X\nY"+(A\n+B|stringify)+"C\nD"');
     });
 
+    it('should not be confused by double quotes, etc. outside mustache',
+       (Interpolate interpolate) {
+      expect(interpolate('"{{A}}"'))
+      .toEqual(r'"\""+(A|stringify)+"\""');
+    });
+
   });
-}
+}