Storage Service: Add use counters for DOM storage read/write.

Bug: 1000932
Change-Id: I0b745dc4a35b3998dfd036f6900dccf5edead399
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786973
Commit-Queue: Staphany Park <staphany@chromium.org>
Auto-Submit: Staphany Park <staphany@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693862}

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

@@ -2399,6 +2399,8 @@ enum WebFeature {
   kV8FileSystemDirectoryHandle_GetSystemDirectory_Method = 3016,
   kNotificationShowTrigger = 3017,
   kWebSocketStreamConstructor = 3018,
+  kDOMStorageRead = 3019,
+  kDOMStorageWrite = 3020,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/modules/storage/storage.idl

@@ -28,9 +28,9 @@
 [ImplementedAs=StorageArea]
 interface Storage {
     [RaisesException=Getter] readonly attribute unsigned long length;
-    [RaisesException] DOMString? key(unsigned long index);
-    [LogActivity, RaisesException] getter DOMString? getItem(DOMString key);
-    [LogActivity, RaisesException] setter void setItem(DOMString key, DOMString value);
-    [LogActivity, RaisesException] deleter void removeItem(DOMString key);
-    [LogActivity, RaisesException] void clear();
+    [RaisesException, MeasureAs=DOMStorageRead] DOMString? key(unsigned long index);
+    [LogActivity, RaisesException, MeasureAs=DOMStorageRead] getter DOMString? getItem(DOMString key);
+    [LogActivity, RaisesException, MeasureAs=DOMStorageWrite] setter void setItem(DOMString key, DOMString value);
+    [LogActivity, RaisesException, MeasureAs=DOMStorageWrite] deleter void removeItem(DOMString key);
+    [LogActivity, RaisesException, MeasureAs=DOMStorageWrite] void clear();
 };

tools/metrics/histograms/enums.xml

@@ -24583,6 +24583,8 @@ Called by update_net_error_codes.py.-->
       label="V8FileSystemDirectoryHandle_GetSystemDirectory_Method"/>
   <int value="3017" label="NotificationShowTrigger"/>
   <int value="3018" label="WebSocketStreamConstructor"/>
+  <int value="3019" label="DOMStorageRead"/>
+  <int value="3020" label="DOMStorageWrite"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">