[heap] Introduce enum of garbage collection reasons.

test/cctest/test-global-handles.cc

Index: test/cctest/test-global-handles.cc
diff --git a/test/cctest/test-global-handles.cc b/test/cctest/test-global-handles.cc
index d6586c61046a7bd7221b7b5e68e254c94a3d5268..d777432f2fe178278d80ac28b86c78d0747d5fe9 100644
--- a/test/cctest/test-global-handles.cc
+++ b/test/cctest/test-global-handles.cc
@@ -352,7 +352,7 @@ TEST(EternalHandles) {
     CHECK(!eternals[i].IsEmpty());
   }
 
-  isolate->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
 
   for (int i = 0; i < kArrayLength; i++) {
     for (int j = 0; j < 2; j++) {
@@ -445,7 +445,7 @@ TEST(FinalizerWeakness) {
     g.SetWeak(&g, finalizer, v8::WeakCallbackType::kFinalizer);
   }
 
-  CcTest::i_isolate()->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
 
   CHECK(!g.IsEmpty());
   v8::HandleScope scope(isolate);
@@ -468,7 +468,7 @@ TEST(PhatomHandlesWithoutCallbacks) {
   }
 
   CHECK_EQ(0, isolate->NumberOfPhantomHandleResetsSinceLastCall());
-  CcTest::i_isolate()->heap()->CollectAllAvailableGarbage();
+  CcTest::CollectAllAvailableGarbage();
   CHECK_EQ(2, isolate->NumberOfPhantomHandleResetsSinceLastCall());
   CHECK_EQ(0, isolate->NumberOfPhantomHandleResetsSinceLastCall());
 }