DevTools: do not report paint metrics under blink.user_timing category.

third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/FirstMeaningfulPaintDetector.h"
 
 #include "core/css/FontFaceSet.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "core/paint/PaintTiming.h"
 #include "platform/Histogram.h"
@@ skipping 81 matching lines @@
   if (m_paintTiming->firstPaint() == 0.0)
     return;
 
   m_provisionalFirstMeaningfulPaint = monotonicallyIncreasingTime();
   m_nextPaintIsMeaningful = false;
 
   if (m_network2QuietReached)
     return;
 
   TRACE_EVENT_MARK_WITH_TIMESTAMP1(
-      "loading", "firstMeaningfulPaintCandidate",
+      "loading,devtools.timeline", "firstMeaningfulPaintCandidate",
       TraceEvent::toTraceTimestamp(m_provisionalFirstMeaningfulPaint), "frame",
       document()->frame());
   // Ignore the first meaningful paint candidate as this generally is the first
   // contentful paint itself.
   if (!m_seenFirstMeaningfulPaintCandidate) {
     m_seenFirstMeaningfulPaintCandidate = true;
     return;
   }
   m_paintTiming->setFirstMeaningfulPaintCandidate(
       m_provisionalFirstMeaningfulPaint);
@@ skipping 108 matching lines @@
   } else if (m_firstMeaningfulPaint2Quiet) {
     hadNetworkQuietHistogram.count(HadNetwork2Quiet);
   }
 }
 
 DEFINE_TRACE(FirstMeaningfulPaintDetector) {
   visitor->trace(m_paintTiming);
 }
 
 }  // namespace blink