Instrument Screen.touchSupport for identifiability study.

This potentially provides a small amount of information that help could
identify a user across sites.

Bug: 973801
Change-Id: Ie9e16755323a4418b2d3109ce4993bcbe0d36a33
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2443549Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Commit-Queue: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812983}

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2829,7 +2829,7 @@ enum WebFeature {
   kV8Document_ElementsFromPoint_Method = 3501,
   kV8ShadowRoot_ElementFromPoint_Method = 3502,
   kV8ShadowRoot_ElementsFromPoint_Method = 3503,
-  kIdentifiabilityStudyReserved3504 = 3504,
+  kWindowScreenTouchSupport = 3504,
   kIdentifiabilityStudyReserved3505 = 3505,
   kIdentifiabilityStudyReserved3506 = 3506,
   kIdentifiabilityStudyReserved3507 = 3507,

third_party/blink/renderer/core/frame/screen.idl

@@ -52,5 +52,5 @@
     [HighEntropy=Direct, MeasureAs=WindowScreenPrimary, RuntimeEnabled=WindowPlacement] readonly attribute boolean primary;
     [RuntimeEnabled=WindowPlacement] readonly attribute float scaleFactor;
     [HighEntropy=Direct, MeasureAs=WindowScreenId, RuntimeEnabled=WindowPlacement] readonly attribute DOMString id;
-    [RuntimeEnabled=WindowPlacement] readonly attribute boolean touchSupport;
+    [HighEntropy=Direct, MeasureAs=WindowScreenTouchSupport, RuntimeEnabled=WindowPlacement] readonly attribute boolean touchSupport;
 };

tools/metrics/histograms/enums.xml

@@ -29347,7 +29347,7 @@ Called by update_use_counter_feature_enum.py.-->
   <int value="3501" label="V8Document_ElementsFromPoint_Method"/>
   <int value="3502" label="V8ShadowRoot_ElementFromPoint_Method"/>
   <int value="3503" label="V8ShadowRoot_ElementsFromPoint_Method"/>
-  <int value="3504" label="IdentifiabilityStudyReserved3504"/>
+  <int value="3504" label="WindowScreenTouchSupport"/>
   <int value="3505" label="IdentifiabilityStudyReserved3505"/>
   <int value="3506" label="IdentifiabilityStudyReserved3506"/>
   <int value="3507" label="IdentifiabilityStudyReserved3507"/>