[DO NOT COMMIT] Trace events for layout-based First Meaningful Paint detection

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index a603be0b0d1f1d196811b4bed1f10d72fa3f2107..c7f49e68bc65f621e777b73327b125be5d58c86f 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -823,7 +823,7 @@ static inline void layoutFromRootObject(LayoutObject& root)
 void FrameView::prepareLayoutAnalyzer()
 {
     bool isTracing = false;
-    TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("blink.debug.layout"), &isTracing);
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED("blink.user_timing", &isTracing);
     if (!isTracing) {
         m_analyzer.clear();
         return;
@@ -839,6 +839,10 @@ PassOwnPtr<TracedValue> FrameView::analyzerCounters()
         return TracedValue::create();
     OwnPtr<TracedValue> value = m_analyzer->toTracedValue();
     value->setString("host", layoutView()->document().location()->host());
+    value->setInteger("visibleHeight", visibleHeight());
+    value->setInteger("contentsHeightBefore", contentsSize().height());

[paulirish, 2016/04/29 02:41:51]

Are you submitting a CL for these non-font counter values?

[Kunihiko Sakamoto, 2016/05/09 07:33:42]

Sorry for the delay, just sent out https://codereview.chromium.org/1957193002/
for review.

+    value->setInteger("contentsHeightAfter", layoutView()->documentRect().height());
+    value->setBoolean("hasBlankText", FontFaceSet::hasBlankText(*m_frame->document()));
     return value.release();
 }
 
@@ -848,7 +852,7 @@ void FrameView::performLayout(bool inSubtreeLayout)
 {
     ASSERT(inSubtreeLayout || m_layoutSubtreeRootList.isEmpty());
 
-    TRACE_EVENT_BEGIN0(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout");
+    TRACE_EVENT_BEGIN0("blink.user_timing", "FrameView::performLayout");
     prepareLayoutAnalyzer();
 
     ScriptForbiddenScope forbidScript;
@@ -888,8 +892,8 @@ void FrameView::performLayout(bool inSubtreeLayout)
 
     lifecycle().advanceTo(DocumentLifecycle::AfterPerformLayout);
 
-    TRACE_EVENT_END1(PERFORM_LAYOUT_TRACE_CATEGORIES, "FrameView::performLayout",
-        "counters", analyzerCounters());
+    TRACE_EVENT_END2("blink.user_timing", "FrameView::performLayout",
+        "counters", analyzerCounters(), "frame", m_frame.get());
 }
 
 void FrameView::scheduleOrPerformPostLayoutTasks()