Ad metrics: Remove PageLoad.Clients.Ads...SqrtNumberOfPixels.

This makes the histogram obsolete and removes the lines that record
and test it.

Bug: 1135308
Change-Id: Ib7704d2a739bee3ff5d65705ec3145055e8cc6ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2468468Reviewed-by: John Delaney <johnidel@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Commit-Queue: Cammie Smith Barnes <cammie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817102}

chrome/browser/page_load_metrics/observers/ad_metrics/ads_page_load_metrics_observer.cc

@@ -1149,12 +1149,6 @@ void AdsPageLoadMetricsObserver::RecordPerFrameHistogramsForAdTagging(
     aggregate_ad_info_by_visibility_[static_cast<int>(visibility)].num_frames +=
         1;
 
-    int frame_area = ad_frame_data.frame_size().GetCheckedArea().ValueOrDefault(
-        std::numeric_limits<int>::max());
-    ADS_HISTOGRAM("FrameCounts.AdFrames.PerFrame.SqrtNumberOfPixels",
-                  UMA_HISTOGRAM_COUNTS_10000, visibility,
-                  std::sqrt(frame_area));
-
     ADS_HISTOGRAM("Bytes.AdFrames.PerFrame.Total2", PAGE_BYTES_HISTOGRAM,
                   visibility, ad_frame_data.bytes());
     ADS_HISTOGRAM("Bytes.AdFrames.PerFrame.Network", PAGE_BYTES_HISTOGRAM,

chrome/browser/page_load_metrics/observers/ad_metrics/ads_page_load_metrics_observer_browsertest.cc

@@ -76,10 +76,6 @@ const char kAdUserActivationHistogramId[] =
     "PageLoad.Clients.Ads.FrameCounts.AdFrames.PerFrame."
     "UserActivation";
 
-const char kSqrtNumberOfPixelsHistogramId[] =
-    "PageLoad.Clients.Ads.FrameCounts.AdFrames.PerFrame."
-    "SqrtNumberOfPixels";
-
 const char kPeakWindowdPercentHistogramId[] =
     "PageLoad.Clients.Ads.Cpu.FullPage.PeakWindowedPercent2";
 
@@ -1118,8 +1114,6 @@ IN_PROC_BROWSER_TEST_F(AdsPageLoadMetricsObserverBrowserTest, FramePixelSize) {
 
   // Navigate away to force the histogram recording.
   ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL));
-  histogram_tester.ExpectBucketCount(kSqrtNumberOfPixelsHistogramId, 100, 2);
-  histogram_tester.ExpectBucketCount(kSqrtNumberOfPixelsHistogramId, 0, 1);
 
   // Verify each UKM entry has a corresponding, unique size.
   auto entries =

tools/metrics/histograms/histograms_xml/obsolete_histograms.xml

@@ -53281,6 +53281,23 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram base="true"
+    name="PageLoad.FrameCounts.AdFrames.PerFrame.SqrtNumberOfPixels"
+    units="pixels" expires_after="2021-01-30">
+  <obsolete>
+    Removed 10/20.
+  </obsolete>
+  <owner>johnidel@chromium.org</owner>
+  <owner>jkarlin@chromium.org</owner>
+  <summary>
+    The square root of the area of a root adframe in pixels. Only recorded for
+    ad frames with non-zero total bytes. Recorded when the page is destroyed or
+    navigated. Display none iframes will not always update their size because
+    they lack a content view. This uses the last size of frame before it was set
+    to display: none.
+  </summary>
+</histogram>
+
 <histogram name="PageLoad.FrameCounts.AnyParentFrame.AdFrames"
     units="Ad frames" expires_after="M80">
   <obsolete>

tools/metrics/histograms/histograms_xml/page/histograms.xml

@@ -1285,20 +1285,6 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
-<histogram base="true"
-    name="PageLoad.FrameCounts.AdFrames.PerFrame.SqrtNumberOfPixels"
-    units="pixels" expires_after="2021-01-30">
-  <owner>johnidel@chromium.org</owner>
-  <owner>jkarlin@chromium.org</owner>
-  <summary>
-    The square root of the area of a root adframe in pixels. Only recorded for
-    ad frames with non-zero total bytes. Recorded when the page is destroyed or
-    navigated. Display none iframes will not always update their size because
-    they lack a content view. This uses the last size of frame before it was set
-    to display: none.
-  </summary>
-</histogram>
-
 <histogram name="PageLoad.FrameCounts.AdFrames.PerFrame.UserActivation"
     enum="AdUserActivationStatus" expires_after="2021-01-17">
   <owner>johnidel@chromium.org</owner>