Report the reason for a garbage collection when verbose GC is enabled.

runtime/vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
 #include "platform/utils.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
@@ skipping 1285 matching lines @@
 
 
 // Helper class to ensure new gen GC is triggered without any side effects.
 // The normal call to CollectGarbage(Heap::kNew) could potentially trigger
 // an old gen collection if there is a promotion failure and this could
 // perturb the test.
 class GCTestHelper : public AllStatic {
  public:
   static void CollectNewSpace(Heap::ApiCallbacks api_callbacks) {
     bool invoke_api_callbacks = (api_callbacks == Heap::kInvokeApiCallbacks);
-    Isolate::Current()->heap()->new_space_->Scavenge(invoke_api_callbacks);
+    Isolate::Current()->heap()->new_space_->Scavenge(invoke_api_callbacks,
+                                                     "test case");
   }
 };
 
 
 // Only ia32 and x64 can run execution tests.
 #if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
 
 TEST_CASE(WeakPersistentHandle) {
   Dart_Handle weak_new_ref = Dart_Null();
   EXPECT(Dart_IsNull(weak_new_ref));
@@ skipping 5205 matching lines @@
   EXPECT(Dart_IsString(str));
   len = -1;
   EXPECT_VALID(Dart_StringLength(str, &len));
   EXPECT_EQ(0, len);
 }
 
 
 #endif  // defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64).
 
 }  // namespace dart