Bind Window focus ability to the ExecutionContext instead of the process.

Source/core/dom/ScopedWindowFocusAllowedIndicator.cpp

+// Copyright 2014 The Chromium 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 "config.h"
+#include "core/dom/ScopedWindowFocusAllowedIndicator.h"
+
+#include "core/dom/ExecutionContext.h"
+
+namespace blink {
+
+ScopedWindowFocusAllowedIndicator::ScopedWindowFocusAllowedIndicator(
+    ExecutionContext* context)
+    : ContextLifecycleObserver(context)
+{
+    if (executionContext())
+        executionContext()->allowWindowFocus();
+}
+
+ScopedWindowFocusAllowedIndicator::~ScopedWindowFocusAllowedIndicator()
+{
+    if (executionContext())
+        executionContext()->consumeWindowFocus();
+}
+
+} // namespace blink