Make updateLayoutAndStyleForPainting() O(N) in terms of frame number in LayoutView::hitTest()

Source/core/layout/LayoutView.cpp

Index: Source/core/layout/LayoutView.cpp
diff --git a/Source/core/layout/LayoutView.cpp b/Source/core/layout/LayoutView.cpp
index 5e23df84c7df259ca348d2fc1a3affc5f916711c..7ce7b13975e77e3ae08e1c3ba583ad8a77d68716 100644
--- a/Source/core/layout/LayoutView.cpp
+++ b/Source/core/layout/LayoutView.cpp
@@ -83,17 +83,21 @@ LayoutView::~LayoutView()
 
 bool LayoutView::hitTest(HitTestResult& result)
 {
-    TRACE_EVENT_BEGIN0("blink,devtools.timeline", "HitTest");
-    m_hitTestCount++;
-
-    ASSERT(!result.hitTestLocation().isRectBasedTest() || result.hitTestRequest().listBased());
-
     // We have to recursively update layout/style here because otherwise, when the hit test recurses
     // into a child document, it could trigger a layout on the parent document, which can destroy DeprecatedPaintLayer
     // that are higher up in the call stack, leading to crashes.
     // Note that Document::updateLayout calls its parent's updateLayout.
-    // FIXME: It should be the caller's responsibility to ensure an up-to-date layout.
     frameView()->updateLayoutAndStyleForPainting();
+    return hitTestNoLayoutAndStyleUpdate(result);
+}
+
+bool LayoutView::hitTestNoLayoutAndStyleUpdate(HitTestResult& result)
+{
+    TRACE_EVENT_BEGIN0("blink,devtools.timeline", "HitTest");
+    m_hitTestCount++;
+
+    ASSERT(!result.hitTestLocation().isRectBasedTest() || result.hitTestRequest().listBased());
+
     commitPendingSelection();
 
     uint64_t domTreeVersion = document().domTreeVersion();