Introduce new API for detecting when the embedder is in foreground/background.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 25a1d58fb9e0ed1f46c389dfee0bdab7e459a10f..d9a6ff5adbde3f911a0f6d5adbebc046e956e704 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5791,6 +5791,18 @@ class V8_EXPORT Isolate {
   int ContextDisposedNotification(bool dependant_context = true);
 
   /**
+   * Optional notification that the isolate switched to the foreground.
+   * V8 uses these notifications to guide heuristics.
+   */
+  void IsolateInForegroundNotification();
+
+  /**
+   * Optional notification that the isolate switched to the background.
+   * V8 uses these notifications to guide heuristics.
+   */
+  void IsolateInBackgroundNotification();
+
+  /**
    * Allows the host application to provide the address of a function that is
    * notified each time code is added, moved or removed.
    *