Initialize all VariableProxy fields in its constructor

Review URL: http://codereview.chromium.org/3330002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5390 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ast.cc

@@ -84,7 +84,10 @@ VariableProxy::VariableProxy(Handle<String> name,
 
 
 VariableProxy::VariableProxy(bool is_this)
-    : is_this_(is_this) {
+  : var_(NULL),
+    is_this_(is_this),
+    inside_with_(false),
+    is_trivial_(false) {
 }