[debugger] correctly find function context.

src/contexts.cc

 // Copyright 2011 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.
 
 #include "src/contexts.h"
 
 #include "src/ast/scopeinfo.h"
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
@@ skipping 61 matching lines @@
 
 Context* Context::declaration_context() {
   Context* current = this;
   while (!current->is_declaration_context()) {
     current = current->previous();
     DCHECK(current->closure() == closure());
   }
   return current;
 }
 
+Context* Context::closure_context() {
+  Context* current = this;
+  while (!current->IsFunctionContext() && !current->IsScriptContext() &&
+         !current->IsNativeContext()) {
+    current = current->previous();
+    DCHECK(current->closure() == closure());
+  }
+  return current;
+}
 
 JSObject* Context::extension_object() {
   DCHECK(IsNativeContext() || IsFunctionContext() || IsBlockContext());
   HeapObject* object = extension();
   if (object->IsTheHole()) return nullptr;
   if (IsBlockContext()) {
     if (!object->IsSloppyBlockWithEvalContextExtension()) return nullptr;
     object = SloppyBlockWithEvalContextExtension::cast(object)->extension();
   }
   DCHECK(object->IsJSContextExtensionObject() ||
@@ skipping 479 matching lines @@
 
   int previous_value = errors_thrown()->value();
   set_errors_thrown(Smi::FromInt(previous_value + 1));
 }
 
 
 int Context::GetErrorsThrown() { return errors_thrown()->value(); }
 
 }  // namespace internal
 }  // namespace v8