[es6] Fix scoping for default parameters in arrow functions

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index 16581d776f09355a099645170a69ce53bb0c18e1..8400094564cff764622a8b159745e33ba56ff14f 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -112,6 +112,11 @@ class Scope: public ZoneObject {
   // tree and its children are reparented.
   Scope* FinalizeBlockScope();
 
+  // Inserts outer_scope into this scope's scope chain (and removes this
+  // from the current outer_scope_'s inner_scopes_).
+  // Assumes outer_scope_ is non-null.
+  void ReplaceOuterScope(Scope* outer_scope);
+
   Zone* zone() const { return zone_; }
 
   // ---------------------------------------------------------------------------
@@ -178,13 +183,19 @@ class Scope: public ZoneObject {
     return proxy;
   }
 
+  void AddUnresolved(VariableProxy* proxy) {
+    DCHECK(!already_resolved());
+    DCHECK(!proxy->is_resolved());
+    unresolved_.Add(proxy, zone_);
+  }
+
   // Remove a unresolved variable. During parsing, an unresolved variable
   // may have been added optimistically, but then only the variable name
   // was used (typically for labels). If the variable was not declared, the
   // addition introduced a new unresolved variable which may end up being
   // allocated globally as a "ghost" variable. RemoveUnresolved removes
   // such a variable again if it was added; otherwise this is a no-op.
-  void RemoveUnresolved(VariableProxy* var);
+  bool RemoveUnresolved(VariableProxy* var);
 
   // Creates a new temporary variable in this scope's TemporaryScope.  The
   // name is only used for printing and cannot be used to find the variable.
@@ -813,6 +824,16 @@ class Scope: public ZoneObject {
     }
   }
 
+  void RemoveInnerScope(Scope* inner_scope) {
+    DCHECK_NOT_NULL(inner_scope);
+    for (int i = 0; i < inner_scopes_.length(); i++) {
+      if (inner_scopes_[i] == inner_scope) {
+        inner_scopes_.Remove(i);
+        break;
+      }
+    }
+  }
+
   void SetDefaults(ScopeType type, Scope* outer_scope,
                    Handle<ScopeInfo> scope_info,
                    FunctionKind function_kind = kNormalFunction);