Put LayoutAnalyzer back behind disabled-by-default-blink.debug.layout.

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 794 matching lines @@
     document->updateLayoutTreeIfNeeded();
     lifecycle().advanceTo(DocumentLifecycle::StyleClean);
 }
 
 static inline void layoutFromRootObject(LayoutObject& root)
 {
     LayoutState layoutState(root);
     root.layout();
 }
 
+void FrameView::prepareLayoutAnalyzer()
+{
+    bool isTracing = false;
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.debug.layout"), &isTracing);
+    if (!isTracing) {
+        m_analyzer.clear();
+        return;
+    }
+    if (!m_analyzer)
+        m_analyzer = adoptPtr(new LayoutAnalyzer());
+    m_analyzer->reset();
+}
+
 PassRefPtr<TracedValue> FrameView::analyzerCounters()
 {
-    RefPtr<TracedValue> value = layoutAnalyzer().toTracedValue();
+    if (!m_analyzer)
+        return TracedValue::create();
+    RefPtr<TracedValue> value = m_analyzer->toTracedValue();
     value->setString("host", layoutView()->document().location()->host());
     return value;
 }
 
 #define PERFORM_LAYOUT_TRACE_CATEGORIES "blink,benchmark," TRACE_DISABLED_BY_DEFAULT("blink.debug.layout")
 
 void FrameView::performLayout(bool inSubtreeLayout)
 {
     ASSERT(inSubtreeLayout || m_layoutSubtreeRoots.isEmpty());
 
     TRACE_EVENT_BEGIN0(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout");
-    layoutAnalyzer().reset();
+    prepareLayoutAnalyzer();
 
     ScriptForbiddenScope forbidScript;
 
     ASSERT(!isInPerformLayout());
     lifecycle().advanceTo(DocumentLifecycle::InPerformLayout);
 
     TemporaryChange<bool> changeInPerformLayout(m_inPerformLayout, true);
 
     // performLayout is the actual guts of layout().
     // FIXME: The 300 other lines in layout() probably belong in other helper functions
     // so that a single human could understand what layout() is actually doing.
 
     forceLayoutParentViewIfNeeded();
 
     if (inSubtreeLayout) {
-        layoutAnalyzer().increment(LayoutAnalyzer::PerformLayoutRootLayoutObjects, m_layoutSubtreeRoots.size());
+        if (m_analyzer)
+            m_analyzer->increment(LayoutAnalyzer::PerformLayoutRootLayoutObjects, m_layoutSubtreeRoots.size());
         while (m_layoutSubtreeRoots.size()) {
             LayoutObject& root = *m_layoutSubtreeRoots.takeAny();
             if (!root.needsLayout())
                 continue;
             layoutFromRootObject(root);
 
             // We need to ensure that we mark up all renderers up to the LayoutView
             // for paint invalidation. This simplifies our code as we just always
             // do a full tree walk.
             if (LayoutObject* container = root.container())
                 container->setMayNeedPaintInvalidation();
         }
     } else {
         layoutFromRootObject(*layoutView());
     }
 
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->updateAllImageResourcePriorities();
 
     lifecycle().advanceTo(DocumentLifecycle::AfterPerformLayout);
 
-    layoutAnalyzer().recordCounters();
+    if (m_analyzer)
+        m_analyzer->recordCounters();
     TRACE_EVENT_END1(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout",
         "counters", analyzerCounters());
 }
 
 void FrameView::scheduleOrPerformPostLayoutTasks()
 {
     if (m_postLayoutTasksTimer.isActive())
         return;
 
     if (!m_inSynchronousPostLayout) {
@@ skipping 3117 matching lines @@
 LayoutObject* FrameView::viewportLayoutObject()
 {
     if (Document* document = frame().document()) {
         if (Element* element = document->viewportDefiningElement())
             return element->layoutObject();
     }
     return nullptr;
 }
 
 } // namespace blink