[compiler] Add a use counter for Turbofan OSR compiles

.. to track how often OSR is used in the real world.

Chromium CL: crrev.com/c/3853648

Bug: v8:13228
Change-Id: I9aee2eefb8a7b479e6ade403f46bfd7eac9ac5cd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3852388Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82685}

include/v8-isolate.h

@@ -540,6 +540,7 @@ class V8_EXPORT Isolate {
     kInvalidatedMegaDOMProtector = 112,
     kFunctionPrototypeArguments = 113,
     kFunctionPrototypeCaller = 114,
+    kTurboFanOsrCompileStarted = 115,
 
     // If you add new values here, you'll also need to update Chromium's:
     // web_feature.mojom, use_counter_callback.cc, and enums.xml. V8 changes to

src/codegen/compiler.cc

@@ -1134,6 +1134,10 @@ MaybeHandle<CodeT> CompileTurbofan(Isolate* isolate,
     job->compilation_info()->set_discard_result_for_testing();
   }
 
+  if (IsOSR(osr_offset)) {
+    isolate->CountUsage(v8::Isolate::kTurboFanOsrCompileStarted);
+  }
+
   // Prepare the job and launch concurrent compilation, or compile now.
   if (IsConcurrent(mode)) {
     if (CompileTurbofan_Concurrent(isolate, std::move(job))) return {};