Move the user interaction policy for FirstMeaningfulPaint UMA into renderer

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

 // Copyright 2015 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/PaintTiming.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/LocalFrameView.h"
 #include "core/loader/DocumentLoader.h"
 #include "core/loader/ProgressTracker.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "core/timing/DOMWindowPerformance.h"
 #include "core/timing/Performance.h"
+#include "platform/Histogram.h"
 #include "platform/WebFrameScheduler.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
 #include "public/platform/WebLayerTreeView.h"
 
 namespace blink {
 
 namespace {
 
 Performance* GetPerformanceInstance(LocalFrame* frame) {
   Performance* performance = nullptr;
@@ skipping 62 matching lines @@
 
 void PaintTiming::SetFirstMeaningfulPaintCandidate(double timestamp) {
   if (first_meaningful_paint_candidate_)
     return;
   first_meaningful_paint_candidate_ = timestamp;
   if (GetFrame() && GetFrame()->View() && !GetFrame()->View()->IsAttached()) {
     GetFrame()->FrameScheduler()->OnFirstMeaningfulPaint();
   }
 }
 
-void PaintTiming::SetFirstMeaningfulPaint(double stamp) {
+void PaintTiming::SetFirstMeaningfulPaint(double stamp,
+                                          bool was_after_user_input) {
   DCHECK_EQ(first_meaningful_paint_, 0.0);
-  first_meaningful_paint_ = stamp;
-  TRACE_EVENT_MARK_WITH_TIMESTAMP1(
+  TRACE_EVENT_MARK_WITH_TIMESTAMP2(
       "loading,rail,devtools.timeline", "firstMeaningfulPaint",
-      TraceEvent::ToTraceTimestamp(first_meaningful_paint_), "frame",
-      GetFrame());
-  NotifyPaintTimingChanged();
-  RegisterNotifySwapTime(PaintEvent::kFirstMeaningfulPaint);
+      TraceEvent::ToTraceTimestamp(stamp), "frame", GetFrame(),
+      "afterUserInput", was_after_user_input);
+
+  // Notify FMP for UMA only if there's no user input before FMP, so that layout
+  // changes caused by user interactions wouldn't be considered as FMP.
+  if (!was_after_user_input) {
+    first_meaningful_paint_ = stamp;
+    NotifyPaintTimingChanged();
+    RegisterNotifySwapTime(PaintEvent::kFirstMeaningfulPaint);
+  }
+
+  ReportUserInputHistogram(was_after_user_input);
+}
+
+void PaintTiming::ReportUserInputHistogram(bool had_input) {
+  enum HadUserInput { kNoUserInput, kHadUserInput, kHadUserInputEnumMax };
+  DEFINE_STATIC_LOCAL(EnumerationHistogram, had_user_input_histogram,

[Bryan McQuade, 2017/06/08 17:47:12]

i'd rather not use PageLoad as the prefix here, as those are only tracked for
loads that are filtered according to page load metrics filtering policy. I don't
want to get into the habit of having other renderer-based page load metrics
either.

A couple ideas:
1. Use PageLoad.Internal namespace, which is used for internal tracking /
debugging metrics for PLM maintainers (seems right), e.g.
PageLoad.Internal.PaintTiming.HadUserInputBeforeFirstMeaningfulPaint - no need
for 'Experimental' here since there is no plan to ever promote such a metrics to
non experimental - it's just intended to be internal

2. use a totally new metrics namespace (up to you, just not PageLoad.*)

[Kunihiko Sakamoto, 2017/06/09 05:48:16]

Thanks for the suggestions, renamed to PageLoad.Internal.

+                      ("PageLoad.Experimental.Renderer.PaintTiming."
+                       "HadUserInputBeforeFirstMeaningfulPaint",
+                       kHadUserInputEnumMax));
+
+  if (GetFrame()->IsMainFrame())
+    had_user_input_histogram.Count(had_input ? kHadUserInput : kNoUserInput);
 }
 
 void PaintTiming::NotifyPaint(bool is_first_paint,
                               bool text_painted,
                               bool image_painted) {
   if (is_first_paint)
     MarkFirstPaint();
   if (text_painted)
     MarkFirstTextPaint();
   if (image_painted)
@@ skipping 74 matching lines @@
       first_contentful_paint_swap_ = timestamp;
       return;
     case PaintEvent::kFirstMeaningfulPaint:
       first_meaningful_paint_swap_ = timestamp;
       return;
   }
   NOTREACHED();
 }
 
 }  // namespace blink