[turbofan] Add counter for disabling of speculation bit

This CL adds a performace counter similar to
https://www.chromestatus.com/metrics/feature/timeline/popularity/2238
to estimate how often speculation is disabled in the wild.

Bug: v8:7216, v8:7127
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I421637b386534da4a3aed549a9665870e3b97eb1
Reviewed-on: https://chromium-review.googlesource.com/827012Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50112}

include/v8.h

@@ -7080,6 +7080,7 @@ class V8_EXPORT Isolate {
     kErrorPrepareStackTrace = 44,
     kErrorStackTraceLimit = 45,
     kWebAssemblyInstantiation = 46,
+    kDeoptimizerDisableSpeculation = 47,
 
     // If you add new values here, you'll also need to update Chromium's:
     // web_feature.mojom, UseCounterCallback.cpp, and enums.xml. V8 changes to

src/deoptimizer.cc

@@ -3842,6 +3842,7 @@ void TranslatedState::VerifyMaterializedObjects() {
 void TranslatedState::DoUpdateFeedback() {
   if (!feedback_vector_handle_.is_null()) {
     CHECK(!feedback_slot_.IsInvalid());
+    isolate()->CountUsage(v8::Isolate::kDeoptimizerDisableSpeculation);
     CallICNexus nexus(feedback_vector_handle_, feedback_slot_);
     nexus.SetSpeculationMode(SpeculationMode::kDisallowSpeculation);
   }