Record parser blocking time for scripts inserted via doc.write

third_party/WebKit/Source/core/dom/DocumentParserTiming.h

 // 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.
 
 #ifndef DocumentParserTiming_h
 #define DocumentParserTiming_h
 
 #include "core/dom/Document.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
@@ skipping 26 matching lines @@
     // document. A single document may have multiple parsers, if e.g. the
     // document is re-opened using document.write. DocumentParserTiming only
     // wants to record parser start and stop time for the first parser. To avoid
     // recording parser start and stop times for re-opened documents, we keep
     // track of whether a parser has been detached, and avoid recording
     // start/stop times for subsequent parsers, after the first parser has been
     // detached.
     void markParserDetached();
 
     // Record a duration of time that the parser yielded due to loading a
-    // script, in seconds. This may be called multiple times, once for each time
-    // the parser yields on a script load.
-    void recordParserBlockedOnScriptLoadDuration(double duration);
+    // script, in seconds. scriptInsertedViaDocumentWrite indicates whether the
+    // script causing blocking was inserted via document.write. This may be
+    // called multiple times, once for each time the parser yields on a script
+    // load.
+    void recordParserBlockedOnScriptLoadDuration(
+        double duration, bool scriptInsertedViaDocumentWrite);
 
     // The getters below return monotonically-increasing seconds, or zero if the
     // given parser event has not yet occurred.  See the comments for
     // monotonicallyIncreasingTime in wtf/CurrentTime.h for additional details.
 
     double parserStart() const { return m_parserStart; }
     double parserStop() const { return m_parserStop; }
 
     // Returns the sum of all blocking script load durations reported via
     // recordParseBlockedOnScriptLoadDuration.
     double parserBlockedOnScriptLoadDuration() const { return m_parserBlockedOnScriptLoadDuration; }
 
+    // Returns the sum of all blocking script load durations due to
+    // document.write reported via recordParseBlockedOnScriptLoadDuration.
+    double parserBlockedOnScriptLoadFromDocumentWriteDuration() const { return m_parserBlockedOnScriptLoadFromDocumentWriteDuration; }

[Charlie Harrison, 2016/04/04 21:33:26]

Can you include a comment that this is a lower bound, because the mechanism for
determining if a script was written by document.write sometimes has false
negatives?

[Bryan McQuade, 2016/04/05 15:14:11]

Done.

+
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit DocumentParserTiming(Document&);
     void notifyDocumentParserTimingChanged();
 
     double m_parserStart = 0.0;
     double m_parserStop = 0.0;
     double m_parserBlockedOnScriptLoadDuration = 0.0;
+    double m_parserBlockedOnScriptLoadFromDocumentWriteDuration = 0.0;
     bool m_parserDetached = false;
 
     Member<Document> m_document;
 };
 
 } // namespace blink
 
 #endif