[heap] Introduce enum of garbage collection reasons.

test/cctest/test-global-handles.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 334 matching lines @@
         .FromJust();
     // Create with internal api
     eternal_handles->Create(
         isolate, *v8::Utils::OpenHandle(*object), &indices[i]);
     // Create with external api
     CHECK(eternals[i].IsEmpty());
     eternals[i].Set(v8_isolate, object);
     CHECK(!eternals[i].IsEmpty());
   }
 
-  isolate->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
 
   for (int i = 0; i < kArrayLength; i++) {
     for (int j = 0; j < 2; j++) {
       HandleScope scope(isolate);
       v8::Local<v8::Value> local;
       if (j == 0) {
         // Test internal api
         local = v8::Utils::ToLocal(eternal_handles->Get(indices[i]));
       } else {
         // Test external api
@@ skipping 72 matching lines @@
   int identity;
 
   {
     v8::HandleScope scope(isolate);
     v8::Local<v8::Object> o = v8::Object::New(isolate);
     identity = o->GetIdentityHash();
     g.Reset(isolate, o);
     g.SetWeak(&g, finalizer, v8::WeakCallbackType::kFinalizer);
   }
 
-  CcTest::i_isolate()->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
 
   CHECK(!g.IsEmpty());
   v8::HandleScope scope(isolate);
   v8::Local<v8::Object> o = v8::Local<v8::Object>::New(isolate, g);
   CHECK_EQ(identity, o->GetIdentityHash());
   CHECK(o->Has(isolate->GetCurrentContext(), v8_str("finalizer")).FromJust());
 }
 
 TEST(PhatomHandlesWithoutCallbacks) {
   CcTest::InitializeVM();
   v8::Isolate* isolate = CcTest::isolate();
 
   v8::Global<v8::Object> g1, g2;
   {
     v8::HandleScope scope(isolate);
     g1.Reset(isolate, v8::Object::New(isolate));
     g1.SetWeak();
     g2.Reset(isolate, v8::Object::New(isolate));
     g2.SetWeak();
   }
 
   CHECK_EQ(0, isolate->NumberOfPhantomHandleResetsSinceLastCall());
-  CcTest::i_isolate()->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
   CHECK_EQ(2, isolate->NumberOfPhantomHandleResetsSinceLastCall());
   CHECK_EQ(0, isolate->NumberOfPhantomHandleResetsSinceLastCall());
 }