[Scheduling APIs] Adding UseCounters for postTask prototype

Adding UseCounters for postTask, TaskController, and TaskSignal now
that the IDLs have settled a bit and we have something we want to OT.

Bug: 979017
Change-Id: I265bfdf9f6ef3217ec2b65abf62f0af0fd2c0da4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017677Reviewed-by: Nate Chapin <japhet@chromium.org>
Commit-Queue: Scott Haseley <shaseley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735002}

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

@@ -2504,6 +2504,10 @@ enum WebFeature {
   kMeasureMemory = 3139,
   kV8Animation_ReplaceState_AttributeGetter = 3140,
   kV8Animation_Persist_Method = 3141,
+  kTaskControllerConstructor = 3142,
+  kTaskControllerSetPriority= 3143,
+  kTaskSignalPriority = 3144,
+  kSchedulerPostTask = 3145,
 
   // 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/scheduler/scheduler.idl

@@ -8,5 +8,5 @@
     ImplementedAs=DOMScheduler,
     RuntimeEnabled=WebScheduler
 ] interface Scheduler {
-    [CallWith=ScriptState, RaisesException] Promise<any> postTask(Function callback, optional SchedulerPostTaskOptions options = {}, any... arguments);
+    [CallWith=ScriptState, MeasureAs=SchedulerPostTask, RaisesException] Promise<any> postTask(Function callback, optional SchedulerPostTaskOptions options = {}, any... arguments);
 };

third_party/blink/renderer/modules/scheduler/task_controller.idl

@@ -7,9 +7,10 @@
 
 [
     ImplementedAs=DOMTaskController,
+    MeasureAs=TaskControllerConstructor,
     RuntimeEnabled=WebScheduler
 ] interface TaskController : AbortController {
     [CallWith=Document] constructor(optional TaskPriority priority = "user-visible");
-    void setPriority(TaskPriority priority);
+    [MeasureAs=TaskControllerSetPriority] void setPriority(TaskPriority priority);
 };
 

third_party/blink/renderer/modules/scheduler/task_signal.idl

@@ -9,5 +9,5 @@
     ImplementedAs=DOMTaskSignal,
     RuntimeEnabled=WebScheduler
 ] interface TaskSignal : AbortSignal {
-  readonly attribute TaskPriority priority;
+  [MeasureAs=TaskSignalPriority] readonly attribute TaskPriority priority;
 };

tools/metrics/histograms/enums.xml

@@ -26041,6 +26041,10 @@ to ensure that the crash string is shown properly on the user-facing crash UI.
   <int value="3139" label="MeasureMemory"/>
   <int value="3140" label="V8Animation_ReplaceState_AttributeGetter"/>
   <int value="3141" label="V8Animation_Persist_Method"/>
+  <int value="3142" label="TaskControllerConstructor"/>
+  <int value="3143" label="TaskControllerSetPriority"/>
+  <int value="3144" label="TaskSignalPriority"/>
+  <int value="3145" label="SchedulerPostTask"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">