Fix compound bindings with braces in literals

src/lib/annotations/annotations.html

@@ -88,7 +88,7 @@ subject to an additional IP rights grant found at http://polymer.github.io/PATEN
           this._parseElementAnnotations(node, list);
     },
 
-    _bindingRegex: /([^{[]*)({{|\[\[)([^}\]]*)(?:]]|}})/g,
+    _bindingRegex: /([^{[]*)(\{\{|\[\[)(?!\}\}|\]\])(.+?)(?:\]\]|\}\})/g,
 
     // TODO(kschaaf): We could modify this to allow an escape mechanism by
     // looking for the escape sequence in each of the matches and converting

test/unit/bind-elements.html

@@ -26,6 +26,7 @@
       no-computed="{{foobared(noInlineComputed)}}"
       compoundAttr1$="{{cpnd1}}{{ cpnd2 }}{{cpnd3.prop}}{{ computeCompound(cpnd4, cpnd5, 'literal')}}"
       compoundAttr2$="literal1 {{cpnd1}} literal2 {{cpnd2}}{{cpnd3.prop}} literal3 {{computeCompound(cpnd4, cpnd5, 'literal')}} literal4"
+      compoundAttr3$="{{computeCompound('world', 'username ', 'Hello {0} ')}}"
       >
       Test
       </div>

test/unit/bind.html

@@ -767,6 +767,12 @@ suite('compound binding / string interpolation', function() {
     assert.equal(el.$.boundChild.getAttribute('compoundAttr2'), 'literal1  literal2  literal3 literal literal4');
   });
 
+  test('compound property attribute with {} in text', function() {
+    var el = document.createElement('x-basic');
+
+    assert.equal(el.$.boundChild.getAttribute('compoundAttr3'), 'Hello {0} username world')
+  })
+
   test('compound adjacent textNode bindings', function() {
     var el = document.createElement('x-basic');
     // The single space is due to the gambit to prevent empty text nodes