Add memory pressure notification API

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/cancelable-task.h"
 #include "src/execution.h"
 #include "src/heap/heap.h"
@@ skipping 11 matching lines @@
 class IncrementalMarking {
  public:
   enum State { STOPPED, SWEEPING, MARKING, COMPLETE };
 
   enum CompletionAction { GC_VIA_STACK_GUARD, NO_GC_VIA_STACK_GUARD };
 
   enum ForceMarkingAction { FORCE_MARKING, DO_NOT_FORCE_MARKING };
 
   enum ForceCompletionAction { FORCE_COMPLETION, DO_NOT_FORCE_COMPLETION };
 
-  enum GCRequestType { COMPLETE_MARKING, FINALIZATION };
+  enum GCRequestType { NONE, COMPLETE_MARKING, FINALIZATION };
 
   struct StepActions {
     StepActions(CompletionAction complete_action_,
                 ForceMarkingAction force_marking_,
                 ForceCompletionAction force_completion_)
         : completion_action(complete_action_),
           force_marking(force_marking_),
           force_completion(force_completion_) {}
 
     CompletionAction completion_action;
@@ skipping 30 matching lines @@
   inline bool IsMarkingIncomplete() { return state() == MARKING; }
 
   inline bool IsComplete() { return state() == COMPLETE; }
 
   inline bool IsReadyToOverApproximateWeakClosure() const {
     return request_type_ == FINALIZATION && !finalize_marking_completed_;
   }
 
   GCRequestType request_type() const { return request_type_; }
 
+  void reset_request_type() { request_type_ = NONE; }
+
   bool CanBeActivated();
 
   bool ShouldActivateEvenWithoutIdleNotification();
 
   bool WasActivated();
 
   void Start(const char* reason = nullptr);
 
   void FinalizeIncrementally();
 
@@ skipping 215 matching lines @@
   GCRequestType request_type_;
 
   IncrementalMarkingJob incremental_marking_job_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_