FirstMeaningfulPaint UMA

third_party/WebKit/Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 222 matching lines @@
 #if ENABLE(ASSERT)
     , m_hasAXObject(false)
     , m_setNeedsLayoutForbidden(false)
 #endif
     , m_bitfields(node)
 {
     // TODO(wangxianzhu): Move this into initialization list when we enable the feature by default.
     if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled())
         m_previousPositionFromPaintInvalidationBacking = uninitializedPaintOffset();
     InstanceCounters::incrementCounter(InstanceCounters::LayoutObjectCounter);
+    if (m_node)

[chrishtr, 2016/08/11 00:43:35]

On every LayoutObject creation? That's expensive.

[Charlie Harrison, 2016/08/11 00:48:57]

It's just upping a counter, right? Or are you more concerned with the pointer
indirection.

[chrishtr, 2016/08/11 00:55:46]

I guess it's ok...

Isn't it already counted by line 242's use of InstanceCounters?

[Charlie Harrison, 2016/08/11 01:01:37]

Good catch. It would be nice to not duplicate this work, but I think the
instance counters are per process instead of per frame. Not sure what the right
answer is here.

[Kunihiko Sakamoto, 2016/08/11 03:50:18]

Yeah the instance counters are process global. We do not want to count layout
objects created in other frames (or even worse, in other tabs).

+        frameView()->incrementLayoutObjectCount();
 }
 
 LayoutObject::~LayoutObject()
 {
     ASSERT(!m_hasAXObject);
     InstanceCounters::decrementCounter(InstanceCounters::LayoutObjectCounter);
 }
 
 bool LayoutObject::isDescendantOf(const LayoutObject* obj) const
 {
@@ skipping 3402 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
     }
 }
 
 #endif