Add StackOverflowError and expose error type to api.

src/mirror-debugger.js

Index: src/mirror-debugger.js
diff --git a/src/mirror-debugger.js b/src/mirror-debugger.js
index 212bb0b9cac370b734011add6baa5a95fef593b5..1e2016e7a12460c9b9de8dab0170f7d530f61f97 100644
--- a/src/mirror-debugger.js
+++ b/src/mirror-debugger.js
@@ -642,6 +642,12 @@ ObjectMirror.prototype.propertyNames = function(kind, limit) {
         %GetLocalPropertyNames(this.value_, PROPERTY_ATTRIBUTES_NONE);
     total += propertyNames.length;
 
+    // TODO(dcarney): handle symbols correctly.
+    // Remove symbols from total.
+    for (var i = 0; i < propertyNames.length; i++) {
+      if (IS_SYMBOL(propertyNames[i])) total--;
+    }
+
     // Get names for named interceptor properties if any.
     if (this.hasNamedInterceptor() && (kind & PropertyKind.Named)) {
       var namedInterceptorNames =
@@ -677,6 +683,7 @@ ObjectMirror.prototype.propertyNames = function(kind, limit) {
   // Copy names for named properties.
   if (kind & PropertyKind.Named) {
     for (var i = 0; index < limit && i < propertyNames.length; i++) {
+      if (IS_SYMBOL(propertyNames[i])) continue;  // Skip symbols.
       names[index++] = propertyNames[i];
     }
   }