Use LocalStyleChange for :hover/:active not affected by descendants.

Source/core/css/HoverUpdateTest.cpp

Index: Source/core/css/HoverUpdateTest.cpp
diff --git a/Source/core/css/HoverUpdateTest.cpp b/Source/core/css/HoverUpdateTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..23845c63b4678e1e140b827a9b27d6cfa46bda15
--- /dev/null
+++ b/Source/core/css/HoverUpdateTest.cpp
@@ -0,0 +1,49 @@
+// 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 "HTMLNames.h"
+#include "core/dom/Element.h"
+#include "core/dom/ElementTraversal.h"
+#include "core/frame/Frame.h"
+#include "core/frame/FrameView.h"
+#include "core/html/HTMLDocument.h"
+#include "core/html/HTMLElement.h"
+#include "core/page/EventHandler.h"
+#include "core/testing/DummyPageHolder.h"
+#include "platform/PlatformMouseEvent.h"
+#include <gtest/gtest.h>
+
+using namespace WebCore;
+
+namespace {
+
+TEST(HoverUpdateTest, AffectedByHoverUpdate)
+{
+    // Check that when hovering the div in the document below, you only get a
+    // single element style recalc.
+
+    OwnPtr<DummyPageHolder> dummyPageHolder = DummyPageHolder::create(IntSize(800, 600));
+    HTMLDocument* document = toHTMLDocument(&dummyPageHolder->document());
+    document->documentElement()->setInnerHTML("<style>div {width:100px;height:100px} div:hover { background-color: green }</style>"
+        "<div>"
+        "<span></span>"
+        "<span></span>"
+        "<span></span>"
+        "<span></span>"
+        "</div>", ASSERT_NO_EXCEPTION);
+
+    document->view()->updateLayoutAndStyleIfNeededRecursive();
+    unsigned startCount = document->styleEngine()->resolverAccessCount();
+
+    PlatformMouseEvent moveEvent(IntPoint(20, 20), IntPoint(20, 20), NoButton, PlatformEvent::MouseMoved, 0, false, false, false, false, currentTime());
+    document->frame()->eventHandler().handleMouseMoveEvent(moveEvent);
+    document->view()->updateLayoutAndStyleIfNeededRecursive();
+
+    unsigned accessCount = document->styleEngine()->resolverAccessCount() - startCount;
+
+    ASSERT_EQ(1U, accessCount);
+}
+
+} // namespace