Replace HeapNumber as doublebox with an explicit MutableHeapNumber.

test/cctest/test-heap-profiler.cc

Index: test/cctest/test-heap-profiler.cc
diff --git a/test/cctest/test-heap-profiler.cc b/test/cctest/test-heap-profiler.cc
index cd34d068860f00319c96c942f876cb0361f378dc..3b8e754e40b73fad2f0d2ca9d0657a302716de07 100644
--- a/test/cctest/test-heap-profiler.cc
+++ b/test/cctest/test-heap-profiler.cc
@@ -1688,7 +1688,7 @@ TEST(GetHeapValueForNode) {
   v8::HandleScope scope(env->GetIsolate());
   v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
 
-  CompileRun("a = { s_prop: \'value\', n_prop: 0.1 };");
+  CompileRun("a = { s_prop: \'value\', n_prop: \'value2\' };");
   const v8::HeapSnapshot* snapshot =
       heap_profiler->TakeHeapSnapshot(v8_str("value"));
   CHECK(ValidateSnapshot(snapshot));
@@ -1709,10 +1709,9 @@ TEST(GetHeapValueForNode) {
   CHECK(js_s_prop == heap_profiler->FindObjectById(s_prop->GetId()));
   const v8::HeapGraphNode* n_prop =
       GetProperty(obj, v8::HeapGraphEdge::kProperty, "n_prop");
-  v8::Local<v8::Number> js_n_prop =
-      js_obj->Get(v8_str("n_prop")).As<v8::Number>();
-  CHECK(js_n_prop->NumberValue() ==
-        heap_profiler->FindObjectById(n_prop->GetId())->NumberValue());
+  v8::Local<v8::String> js_n_prop =
+      js_obj->Get(v8_str("n_prop")).As<v8::String>();
+  CHECK(js_n_prop == heap_profiler->FindObjectById(n_prop->GetId()));
 }