Make idle tasks optional in the default platform.

include/libplatform/libplatform.h

Index: include/libplatform/libplatform.h
diff --git a/include/libplatform/libplatform.h b/include/libplatform/libplatform.h
index cab467fd50704f6ddc35dcae46e8f0a68e8b515e..55a10204ee2c11b805a0adbebb0ffa9e77523cc9 100644
--- a/include/libplatform/libplatform.h
+++ b/include/libplatform/libplatform.h
@@ -12,6 +12,8 @@
 namespace v8 {
 namespace platform {
 
+enum class IdleTaskSupport { kDisabled, kEnabled };
+
 /**
  * Returns a new instance of the default v8::Platform implementation.
  *
@@ -19,9 +21,13 @@ namespace platform {
  * is the number of worker threads to allocate for background jobs. If a value
  * of zero is passed, a suitable default based on the current number of
  * processors online will be chosen.
+ * If |idle_task_support| is enabled then the platform will accept idle
+ * tasks (IdleTasksEnabled will return true) and will rely on the embedder
+ * calling v8::platform::RunIdleTasks to process the idle tasks.
  */
 V8_PLATFORM_EXPORT v8::Platform* CreateDefaultPlatform(
-    int thread_pool_size = 0);
+    int thread_pool_size = 0,
+    IdleTaskSupport idle_task_support = IdleTaskSupport::kDisabled);
 
 /**
  * Pumps the message loop for the given isolate.