Bucket FirstContentfulPaint timing into High/Low res clock buckets

components/page_load_metrics/browser/metrics_web_contents_observer.cc

 // 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 "components/page_load_metrics/browser/metrics_web_contents_observer.h"
 
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics.h"
@@ skipping 261 matching lines @@
     } else {
       PAGE_LOAD_HISTOGRAM(kBackgroundHistogramFirstImagePaint,
                           timing_.first_image_paint);
     }
   }
   base::TimeDelta first_contentful_paint = GetFirstContentfulPaint(timing_);
   if (!first_contentful_paint.is_zero()) {
     if (first_contentful_paint < background_delta) {
       PAGE_LOAD_HISTOGRAM(kHistogramFirstContentfulPaint,
                           first_contentful_paint);
+      // Bucket these histograms into high/low resolution clock systems. This
+      // might point us to directions that will de-noise some UMA.
+      if (base::TimeTicks::IsHighResolution()) {
+        PAGE_LOAD_HISTOGRAM(kHistogramFirstContentfulPaintHigh,
+                            first_contentful_paint);
+      } else {
+        PAGE_LOAD_HISTOGRAM(kHistogramFirstContentfulPaintLow,
+                            first_contentful_paint);
+      }
     } else {
       PAGE_LOAD_HISTOGRAM(kBackgroundHistogramFirstContentfulPaint,
                           first_contentful_paint);
     }
   }
 
   // Log time to first foreground / time to first background. Log counts that we
   // started a relevant page load in the foreground / background.
   if (!background_time_.is_null()) {
     PAGE_LOAD_HISTOGRAM(kHistogramFirstBackground, background_delta);
@@ skipping 233 matching lines @@
 
   if (!committed_load_->UpdateTiming(timing)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).
     // We expect this to be a rare occurrence.
     RecordInternalError(ERR_BAD_TIMING_IPC);
   }
 }
 
 }  // namespace page_load_metrics