Provide a counter for thrown JavaScript errors per context

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
@@ skipping 352 matching lines @@
 static void SetObjectPrototype(Handle<JSObject> object, Handle<Object> proto) {
   // object.__proto__ = proto;
   Handle<Map> old_map = Handle<Map>(object->map());
   Handle<Map> new_map = Map::Copy(old_map, "SetObjectPrototype");
   Map::SetPrototype(new_map, proto, FAST_PROTOTYPE);
   JSObject::MigrateToMap(object, new_map);
 }
 
 
 void Bootstrapper::DetachGlobal(Handle<Context> env) {
+  env->GetIsolate()->counters()->errors_thrown_per_context()->AddSample(
+    env->GetErrorsThrown());
+
   Factory* factory = env->GetIsolate()->factory();
   Handle<JSGlobalProxy> global_proxy(JSGlobalProxy::cast(env->global_proxy()));
   global_proxy->set_native_context(*factory->null_value());
   SetObjectPrototype(global_proxy, factory->null_value());
   global_proxy->map()->SetConstructor(*factory->null_value());
   if (FLAG_track_detached_contexts) {
     env->GetIsolate()->AddDetachedContext(env);
   }
 }
 
@@ skipping 2815 matching lines @@
 
     if (!InstallNatives(context_type)) return;
 
     MakeFunctionInstancePrototypeWritable();
 
     if (context_type != THIN_CONTEXT) {
       if (!InstallExtraNatives()) return;
       if (!ConfigureGlobalObjects(global_proxy_template)) return;
     }
     isolate->counters()->contexts_created_from_scratch()->Increment();
+    // Re-initialize the counter because it got incremented during snapshot
+    // creation.
+    isolate->native_context()->set_errors_thrown(Smi::FromInt(0));
   }
 
   // Install experimental natives. Do not include them into the
   // snapshot as we should be able to turn them off at runtime. Re-installing
   // them after they have already been deserialized would also fail.
   if (context_type == FULL_CONTEXT) {
     if (!isolate->serializer_enabled()) {
       InitializeExperimentalGlobal();
       if (!InstallExperimentalNatives()) return;
 
@@ skipping 44 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8