[heap] Introduce enum of garbage collection reasons.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 2dfe4a75a3ae9cbc349eef99623cb707bd2a3d6c..3c4a3774cb630c8af434ab9f0f49bc2d26adab3e 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -37,13 +37,15 @@ namespace internal {
     RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)                                 \
     /* Two GCs before panicking.  In newspace will almost always succeed. */  \
     for (int __i__ = 0; __i__ < 2; __i__++) {                                 \
-      (ISOLATE)->heap()->CollectGarbage(__allocation__.RetrySpace(),          \
-                                        "allocation failure");                \
+      (ISOLATE)->heap()->CollectGarbage(                                      \
+          __allocation__.RetrySpace(),                                        \
+          GarbageCollectionReason::kAllocationFailure);                       \
       __allocation__ = FUNCTION_CALL;                                         \
       RETURN_OBJECT_UNLESS_RETRY(ISOLATE, TYPE)                               \
     }                                                                         \
     (ISOLATE)->counters()->gc_last_resort_from_handles()->Increment();        \
-    (ISOLATE)->heap()->CollectAllAvailableGarbage("last resort gc");          \
+    (ISOLATE)->heap()->CollectAllAvailableGarbage(                            \
+        GarbageCollectionReason::kLastResort);                                \
     {                                                                         \
       AlwaysAllocateScope __scope__(ISOLATE);                                 \
       __allocation__ = FUNCTION_CALL;                                         \
@@ -54,7 +56,6 @@ namespace internal {
     return Handle<TYPE>();                                                    \
   } while (false)
 
-
 template<typename T>
 Handle<T> Factory::New(Handle<Map> map, AllocationSpace space) {
   CALL_HEAP_FUNCTION(