Fix use of history timers in background threads.

src/isolate.h

 // Copyright 2012 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.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <memory>
 #include <queue>
 
@@ skipping 853 matching lines @@
   ISOLATE_INIT_ARRAY_LIST(GLOBAL_ARRAY_ACCESSOR)
 #undef GLOBAL_ARRAY_ACCESSOR
 
 #define NATIVE_CONTEXT_FIELD_ACCESSOR(index, type, name) \
   inline Handle<type> name();                            \
   inline bool is_##name(type* value);
   NATIVE_CONTEXT_FIELDS(NATIVE_CONTEXT_FIELD_ACCESSOR)
 #undef NATIVE_CONTEXT_FIELD_ACCESSOR
 
   Bootstrapper* bootstrapper() { return bootstrapper_; }
+  // Use for updating counters on a foreground thread.
   Counters* counters() {
-    // Call InitializeLoggingAndCounters() if logging is needed before
-    // the isolate is fully initialized.
+    DCHECK(!IsIsolateInBackground());
+    // Make sure InitializeCounters() has been called.
     DCHECK_NOT_NULL(counters_shared_.get());
     return counters_shared_.get();
   }
-  std::shared_ptr<Counters> counters_shared() { return counters_shared_; }
+  // Use for updating counters on a background thread.
+  std::shared_ptr<Counters> counters_shared() {

[Mircea Trofin, 2017/06/22 18:42:24]

nit: shared_counters?

[kschimpf, 2017/06/22 20:38:31]

Actually, to make clear it's context, I'll rename it to async_counters().

+    DCHECK(!IsIsolateInBackground());
+    // Make sure InitializeCounters() has been called.
+    DCHECK_NOT_NULL(counters_shared_.get());
+    return counters_shared_;
+  }
   RuntimeProfiler* runtime_profiler() { return runtime_profiler_; }
   CompilationCache* compilation_cache() { return compilation_cache_; }
   Logger* logger() {
     // Call InitializeLoggingAndCounters() if logging is needed before
     // the isolate is fully initialized.
     DCHECK_NOT_NULL(logger_);
     return logger_;
   }
   StackGuard* stack_guard() { return &stack_guard_; }
   Heap* heap() { return &heap_; }
@@ skipping 940 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_