[wasm] Use counters for shared memory & threads

This the Chromium side of adding usage counter for WASM language
features. It depends on https://chromium-review.googlesource.com/c/v8/v8/+/1186721

R=ahaas@chromium.org, rmcilroy@chromium.org

Bug: chromium:868844
Change-Id: I3e8ed00300a77e7d1f5a44a4ff30ad555051ca21
Reviewed-on: https://chromium-review.googlesource.com/1186726
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585794}

third_party/blink/public/platform/web_feature.mojom

@@ -1985,6 +1985,8 @@ enum WebFeature {
   kReportingObserver = 2529,
   kDeprecationReport = 2530,
   kInterventionReport = 2531,
+  kV8WasmSharedMemory = 2532,
+  kV8WasmThreadOpcodes = 2533,
 
   // 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/bindings/core/v8/use_counter_callback.cc

@@ -151,6 +151,12 @@ void UseCounterCallback(v8::Isolate* isolate,
     case v8::Isolate::kFunctionTokenOffsetTooLongForToString:
       blink_feature = WebFeature::kV8FunctionTokenOffsetTooLongForToString;
       break;
+    case v8::Isolate::kWasmSharedMemory:
+      blink_feature = WebFeature::kV8WasmSharedMemory;
+      break;
+    case v8::Isolate::kWasmThreadOpcodes:
+      blink_feature = WebFeature::kV8WasmThreadOpcodes;
+      break;
     default:
       // This can happen if V8 has added counters that this version of Blink
       // does not know about. It's harmless.

tools/metrics/histograms/enums.xml

@@ -19828,6 +19828,8 @@ Called by update_net_error_codes.py.-->
   <int value="2529" label="ReportingObserver"/>
   <int value="2530" label="DeprecationReport"/>
   <int value="2531" label="InterventionReport"/>
+  <int value="2532" label="V8WasmSharedMemory"/>
+  <int value="2533" label="V8WasmThreadOpcodes"/>
 </enum>
 
 <enum name="FeedbackSource">