Remove unused histogram WebCore.Animation.CSSProperties

This was replaced by Blink.UseCounter.CSSProperties in crbug.com/458925,
and is no longer used.

Bug: 838487
Change-Id: I74adf77c7c291487fd0aed6a40646016aa6fa6b1
Reviewed-on: https://chromium-review.googlesource.com/1228786Reviewed-by: Ali Juma <ajuma@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592425}

third_party/blink/renderer/core/animation/css/css_animations.cc

@@ -135,17 +135,10 @@ StringKeyframeEffectModel* CreateKeyframeEffectModel(
     }
   }
 
-  DEFINE_STATIC_LOCAL(SparseHistogram, property_histogram,
-                      ("WebCore.Animation.CSSProperties"));
   for (const CSSProperty* property : specified_properties_for_use_counter) {
     DCHECK(isValidCSSPropertyID(property->PropertyID()));
     UseCounter::CountAnimatedCSS(element_for_scoping->GetDocument(),
                                  property->PropertyID());
-
-    // TODO(crbug.com/458925): Remove legacy histogram and counts
-    property_histogram.Sample(
-        UseCounter::MapCSSPropertyIdToCSSSampleIdForHistogram(
-            property->PropertyID()));
   }
 
   // Merge duplicate keyframes.
@@ -613,13 +606,6 @@ void CSSAnimations::MaybeApplyPendingUpdate(Element* element) {
     DCHECK(isValidCSSPropertyID(property.GetCSSProperty().PropertyID()));
     UseCounter::CountAnimatedCSS(element->GetDocument(),
                                  property.GetCSSProperty().PropertyID());
-
-    // TODO(crbug.com/458925): Remove legacy histogram and counts
-    DEFINE_STATIC_LOCAL(SparseHistogram, property_histogram,
-                        ("WebCore.Animation.CSSProperties"));
-    property_histogram.Sample(
-        UseCounter::MapCSSPropertyIdToCSSSampleIdForHistogram(
-            property.GetCSSProperty().PropertyID()));
   }
   ClearPendingUpdate();
 }

tools/metrics/histograms/histograms.xml

@@ -114538,6 +114538,10 @@ uploading your change for review.
 </histogram>
 
 <histogram name="WebCore.Animation.CSSProperties" enum="MappedCSSProperties">
+  <obsolete>
+    This has been superseded by Blink.UseCounter.CSSProperties which does not
+    count multiple times per page load. See https://crbug.com/458925.
+  </obsolete>
   <owner>ajuma@chromium.org</owner>
   <summary>
     Counts the number of times each CSS property is animated. There is no limit