[heap] Cleanup and fix GC flags / add testing infra

src/heap/incremental-marking.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_INCREMENTAL_MARKING_H_
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 #include "src/execution.h"
 #include "src/heap/mark-compact.h"
 #include "src/objects.h"
@@ skipping 63 matching lines @@
   }
 
   GCRequestType request_type() const { return request_type_; }
 
   bool CanBeActivated();
 
   bool ShouldActivateEvenWithoutIdleNotification();
 
   bool WasActivated();
 
-  void Start(int mark_compact_flags,
+  void Start(int flags,
              const GCCallbackFlags gc_callback_flags = kNoGCCallbackFlags,
              const char* reason = nullptr);
 
   void MarkObjectGroups();
 
   void UpdateMarkingDequeAfterScavenge();
 
   void Hurry();
 
   void Finalize();
@@ skipping 165 matching lines @@
   GCRequestType request_type_;
 
   GCCallbackFlags gc_callback_flags_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_