Add a use-counter for viewport-fixed position:fixed under a filter

This will inform whether we can make the change suggested in w3c/fxtf-drafts#11 BUG=711736 CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2 Review-Url: https://codereview.chromium.org/2817583006 Cr-Commit-Position: refs/heads/master@{#464853}
mirror · Apr 15, 2017 · e208bf0 · e208bf0
1 parent 097db1d
commit e208bf0
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diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1574,6 +1574,7 @@ class CORE_EXPORT UseCounter {
     kMediaStreamConstraintsGoogDAEchoCancellation = 1958,
     kMediaStreamConstraintsGoogNoiseReduction = 1959,
     kMediaStreamConstraintsGoogPowerLineFrequency = 1960,
+    kViewportFixedPositionUnderFilter = 1961,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.

diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp
@@ -186,6 +186,13 @@ void CompositingInputsUpdater::UpdateRecursive(PaintLayer* layer,
                                        : parent->FilterAncestor();
       bool layer_is_fixed_position =
           layer->GetLayoutObject().Style()->GetPosition() == EPosition::kFixed;
+
+      if (layer_is_fixed_position && properties.filter_ancestor &&
+          layer->FixedToViewport()) {
+        UseCounter::Count(layer->GetLayoutObject().GetDocument(),
+                          UseCounter::kViewportFixedPositionUnderFilter);
+      }
+
       properties.nearest_fixed_position_layer =
           layer_is_fixed_position ? layer : parent->NearestFixedPositionLayer();
 

diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
@@ -95629,6 +95629,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1958" label="MediaStreamConstraintsGoogDAEchoCancellation"/>
   <int value="1959" label="MediaStreamConstraintsGoogNoiseReduction"/>
   <int value="1960" label="MediaStreamConstraintsGoogPowerLineFrequency"/>
+  <int value="1961" label="ViewportFixedPositionUnderFilter"/>
 </enum>
 
 <enum name="FetchRequestMode" type="int">