Handle symbols in FrameMirror#invocationText().

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index adf5133da5e9f7961d8017f5c634f612de498659..b25bc829947ef9bf0579cc37f5cb287673fb5cdd 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -1499,6 +1499,12 @@ PropertyMirror.prototype.name = function() {
 };
 
 
+PropertyMirror.prototype.toText = function() {
+  if (IS_SYMBOL(this.name_)) return %Call(SymbolToString, this.name_);
+  return this.name_;
+};
+
+
 PropertyMirror.prototype.isIndexed = function() {
   for (var i = 0; i < this.name_.length; i++) {
     if (this.name_[i] < '0' || '9' < this.name_[i]) {
@@ -2034,10 +2040,10 @@ FrameMirror.prototype.invocationText = function() {
         if (display_receiver) {
           result += '.';
         }
-        result += property.name();
+        result += property.toText();
       } else {
         result += '[';
-        result += property.name();
+        result += property.toText();
         result += ']';
       }
       // Also known as - if the name in the function doesn't match the name