Introduce an API mirroring the gc extension

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index c56295ac78dd8a4c6561f97f12717e5972381520..ba0487b91519812b1ab1a979bac5760098b772a7 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -3973,6 +3973,15 @@ class V8_EXPORT Isolate {
   };
 
   /**
+   * Types of garbage collections that can be requested via
+   * RequestGarbageCollectionForTesting.
+   */
+  enum GarbageCollectionType {
+    kFullGarbageCollection,
+    kMinorGarbageCollection
+  };
+
+  /**
    * Creates a new isolate.  Does not change the currently entered
    * isolate.
    *
@@ -4184,6 +4193,17 @@ class V8_EXPORT Isolate {
    */
   void ClearInterrupt();
 
+  /**
+   * Request garbage collection in this Isolate. It is only valid to call this
+   * function if --expose_gc was specified.
+   *
+   * This should only be used for testing purposes and not to enforce a garbage
+   * collection schedule. It has strong negative impact on the garbage
+   * collection performance. Use IdleNotification() or LowMemoryNotification()
+   * instead to influence the garbage collection schedule.
+   */
+  void RequestGarbageCollectionForTesting(GarbageCollectionType type);
+
  private:
   Isolate();
   Isolate(const Isolate&);