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

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index 957f41cbf5f5c4b1a7da913de325bd673447235d..fd84693d678fdf490fa9c1c2c242bfd341771f6b 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -812,9 +812,24 @@ static inline void layoutFromRootObject(LayoutObject& 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.get())

[esprehn, 2015/04/30 23:32:35]

You don't need to call get(), you can just test it with !. OwnPtr is convertable
to a bool.

[benjhayden, 2015/04/30 23:55:33]

Done.

+        m_analyzer = adoptPtr(new LayoutAnalyzer());
+    m_analyzer->reset();
+}
+
 PassRefPtr<TracedValue> FrameView::analyzerCounters()
 {
-    RefPtr<TracedValue> value = layoutAnalyzer().toTracedValue();
+    if (!layoutAnalyzer())
+        return TracedValue::create();
+    RefPtr<TracedValue> value = layoutAnalyzer()->toTracedValue();
     value->setString("host", layoutView()->document().location()->host());
     return value;
 }
@@ -826,7 +841,7 @@ void FrameView::performLayout(bool inSubtreeLayout)
     ASSERT(inSubtreeLayout || m_layoutSubtreeRoots.isEmpty());
 
     TRACE_EVENT_BEGIN0(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout");
-    layoutAnalyzer().reset();
+    prepareLayoutAnalyzer();
 
     ScriptForbiddenScope forbidScript;
 
@@ -842,7 +857,8 @@ void FrameView::performLayout(bool inSubtreeLayout)
     forceLayoutParentViewIfNeeded();
 
     if (inSubtreeLayout) {
-        layoutAnalyzer().increment(LayoutAnalyzer::PerformLayoutRootLayoutObjects, m_layoutSubtreeRoots.size());
+        if (layoutAnalyzer())

[esprehn, 2015/04/30 23:32:35]

if (LayoutAnalyzer* analyzer = layoutAnalyzer())
  analyzer->...()

is the usual pattern for this kind of thing. Since this is a simple getter it's
not as important though.

[benjhayden, 2015/04/30 23:55:33]

Changed to m_analyzer.

+            layoutAnalyzer()->increment(LayoutAnalyzer::PerformLayoutRootLayoutObjects, m_layoutSubtreeRoots.size());
         while (m_layoutSubtreeRoots.size()) {
             LayoutObject& root = *m_layoutSubtreeRoots.takeAny();
             if (!root.needsLayout())
@@ -863,7 +879,8 @@ void FrameView::performLayout(bool inSubtreeLayout)
 
     lifecycle().advanceTo(DocumentLifecycle::AfterPerformLayout);
 
-    layoutAnalyzer().recordCounters();
+    if (layoutAnalyzer())
+        layoutAnalyzer()->recordCounters();
     TRACE_EVENT_END1(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout",
         "counters", analyzerCounters());
 }