[platform] Add NumberOfAvailableBackgroundThreads

include/v8-platform.h

Index: include/v8-platform.h
diff --git a/include/v8-platform.h b/include/v8-platform.h
index 4fbef0f5d96bb49ce6a473d715145f614023224a..c46a4d192fb818efbd1b810770b1f3f992d36431 100644
--- a/include/v8-platform.h
+++ b/include/v8-platform.h
@@ -56,6 +56,12 @@ class Platform {
   virtual ~Platform() {}
 
   /**
+   * Gets the number of threads that are used to execute background tasks. Can
+   * be used to limit parallelism in V8.

[jochen (gone - plz use gerrit), 2016/02/05 08:27:07]

I'd remove the "Can be used to limit..." sentence (because it's not true, e.g.,
if the method returns 0, we still post tasks).

You could say that this is used to estimate into how many work packages certain
tasks will be split up.

[jochen (gone - plz use gerrit), 2016/02/05 08:27:53]

and maybe explain what 0 means. I'd guess it means ignore this value, and just
post what you feel is right. The platform always has to be able to execute
background tasks.

[Michael Lippautz, 2016/02/05 09:15:34]

Done.

[Michael Lippautz, 2016/02/05 09:15:34]

Done.

+   */
+  virtual int NumberOfAvailableBackgroundThreads() { return 0; }

[jochen (gone - plz use gerrit), 2016/02/05 08:27:07]

size_t

[Michael Lippautz, 2016/02/05 09:15:34]

Done.

+
+  /**
    * Schedules a task to be invoked on a background thread. |expected_runtime|
    * indicates that the task will run a long time. The Platform implementation
    * takes ownership of |task|. There is no guarantee about order of execution