Add memory pressure interrupt for memory pressure notification

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 62319203f418c4522b103b3d54ced4e43f09971b..49aa9c5a54d0ff3af21db25b56cd86624dc4338b 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5875,6 +5875,12 @@ class V8_EXPORT Isolate {
   void RequestInterrupt(InterruptCallback callback, void* data);
 
   /**
+   * Request V8 to interrupt long running JavaScript code and do GC,
+   * when system memory is pressured.
+   */
+  void RequestMemoryPressureInterrupt();

[jochen (gone - plz use gerrit), 2016/03/09 15:18:59]

I'd prefer an API ReportMemoryPressure(level) where level is an enum class
MemoryPressureLevel { kNone, kModerate, kCritical}

internally, we could just clear the interrupt request for none and do a low
memory gc for moderate / critical

+
+  /**
    * Request garbage collection in this Isolate. It is only valid to call this
    * function if --expose_gc was specified.
    *
@@ -6027,6 +6033,12 @@ class V8_EXPORT Isolate {
   void LowMemoryNotification();
 
   /**
+   * Optional notification that memory pressure interrupt is requested.
+   * V8 uses these notifications to attempt to free memory.
+   */
+  void GCNotificationBasedOnMemoryPressureInterrupt();

[jochen (gone - plz use gerrit), 2016/03/09 15:18:59]

that shouldn't be required

+
+  /**
    * Optional notification that a context has been disposed. V8 uses
    * these notifications to guide the GC heuristic. Returns the number
    * of context disposals - including this one - since the last time