Renderer.LineLayoutMs UMA histogram to measure line layout time.

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 815 matching lines @@
         document->styleResolverChanged();
         document->mediaQueryAffectingValueChanged();
     } else {
         document->evaluateMediaQueryList();
     }
 
     document->updateRenderTreeIfNeeded();
     lifecycle().advanceTo(DocumentLifecycle::StyleClean);
 }
 
+void FrameView::lineLayoutTime(double ms)
+{
+    m_lineLayoutMs += ms;
+}
+
 void FrameView::performLayout(RenderObject* rootForThisLayout, bool inSubtreeLayout)
 {
+    m_lineLayoutMs = 0;
     TRACE_EVENT0("blink,benchmark", "FrameView::performLayout");
     double start = WTF::currentTimeMS();
 
     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.
 
     LayoutState layoutState(*rootForThisLayout);
 
     forceLayoutParentViewIfNeeded();
 
     // FIXME (crbug.com/256657): Do not do two layouts for text autosizing.
     rootForThisLayout->layout();
     gatherDebugLayoutRects(rootForThisLayout);
 
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->updateAllImageResourcePriorities();
 
     lifecycle().advanceTo(DocumentLifecycle::AfterPerformLayout);
     int layoutMs = (WTF::currentTimeMS() - start);
     Platform::current()->histogramCustomCounts("Renderer.LayoutMs", layoutMs, 0, 1000 * 60, 50);
+    Platform::current()->histogramCustomCounts("Renderer.LineLayoutMs", m_lineLayoutMs, 0, 1000 * 60, 50);
 }
 
 void FrameView::scheduleOrPerformPostLayoutTasks()
 {
     if (m_postLayoutTasksTimer.isActive())
         return;
 
     if (!m_inSynchronousPostLayout) {
         m_inSynchronousPostLayout = true;
         // Calls resumeScheduledEvents()
@@ skipping 3167 matching lines @@
 {
     Settings* settings = frame().settings();
     if (!settings || !settings->rootLayerScrolls())
         return this;
 
     RenderView* renderView = this->renderView();
     return renderView ? renderView->scrollableArea() : nullptr;
 }
 
 } // namespace blink