Use invalidation sets for :hover, :active, and :focus.

Source/core/css/HoverUpdateTest.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 "HTMLNames.h"
 #include "core/dom/Element.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 28 matching lines @@
 
     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);
 }
 
+TEST(HoverUpdateTest, ChildrenAffectedByHoverUpdate)
+{
+    // Check that when hovering the div in the document below, you only get a
+    // style recalc for the hovered element and the class=a span. This requires
+    // supporting a descendant invalidation set for :hover.
+
+    OwnPtr<DummyPageHolder> dummyPageHolder = DummyPageHolder::create(IntSize(800, 600));
+    HTMLDocument* document = toHTMLDocument(&dummyPageHolder->document());
+    document->documentElement()->setInnerHTML("<style>div {width:100px;height:100px} div:hover .a { background-color: green }</style>"
+        "<div>"
+        "<span class='a'></span>"
+        "<span></span>"
+        "<span></span>"

[esprehn, 2014/04/04 22:48:27]

Why not a regular layout test like we did for all the other ones?

[rune, 2014/04/08 16:28:25]

Because hover/active/focus changes are synchronously recalculated and cannot be
caught by internals.updateStyleAndReturnAffectedElementCount(). I'm looking at
how to fix the synchronous update.

[rune, 2014/04/10 12:42:12]

I've landed removal of the synchronous update for hover/active now and added a
layout test for hover. Do you want me to remove this?

+        "<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(2U, accessCount);
+}
+
 } // namespace