[heap] Introduce enum of garbage collection reasons.

src/profiler/sampling-heap-profiler.cc

 // Copyright 2015 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.
 
 #include "src/profiler/sampling-heap-profiler.h"
 
 #include <stdint.h>
 #include <memory>
 #include "src/api.h"
 #include "src/base/ieee754.h"
@@ skipping 241 matching lines @@
   for (auto it : node->children_) {
     current->children.push_back(
         TranslateAllocationNode(profile, it.second, scripts));
   }
   node->pinned_ = false;
   return current;
 }
 
 v8::AllocationProfile* SamplingHeapProfiler::GetAllocationProfile() {
   if (flags_ & v8::HeapProfiler::kSamplingForceGC) {
-    isolate_->heap()->CollectAllGarbage(Heap::kNoGCFlags,
-                                        "SamplingHeapProfiler");
+    isolate_->heap()->CollectAllGarbage(
+        Heap::kNoGCFlags, GarbageCollectionReason::kSamplingProfiler);
   }
   // To resolve positions to line/column numbers, we will need to look up
   // scripts. Build a map to allow fast mapping from script id to script.
   std::map<int, Handle<Script>> scripts;
   {
     Script::Iterator iterator(isolate_);
     while (Script* script = iterator.Next()) {
       scripts[script->id()] = handle(script);
     }
   }
   auto profile = new v8::internal::AllocationProfile();
   TranslateAllocationNode(profile, &profile_root_, scripts);
   return profile;
 }
 
 
 }  // namespace internal
 }  // namespace v8