Context-allocate all parameters in generators

Generator function scopes have forced context allocation.  Ensure that
all variables in such scopes get context allocation -- even unused
variables.

This fixes an assertion when reifying generator scopes in the debugger.

R=yangguo@chromium.org
LOG=Y
BUG=v8:3280

Review URL: https://codereview.chromium.org/246733003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20883 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/scopes.cc

@@ -1266,7 +1266,7 @@ void Scope::AllocateParameterLocals() {
   for (int i = params_.length() - 1; i >= 0; --i) {
     Variable* var = params_[i];
     ASSERT(var->scope() == this);
-    if (uses_sloppy_arguments) {
+    if (uses_sloppy_arguments || has_forced_context_allocation()) {
       // Force context allocation of the parameter.
       var->ForceContextAllocation();
     }

test/mjsunit/regress/regress-3280.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-generators --expose-debug-as debug
+
+var Debug = debug.Debug;
+
+var listener_called;
+
+function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.Break) {
+    listener_called = true;
+    exec_state.frame().allScopes();
+  }
+}
+
+Debug.setListener(listener);
+
+function *generator_local_2(a) {
+  debugger;
+}
+generator_local_2(1).next();
+
+assertTrue(listener_called, "listener not called");