[turbofan] Add JSHeapBroker::Trace helper function for logging.

Bug: v8:7790
Change-Id: I1da64ab7f2385be9d62542166a2577cc135b2154
Reviewed-on: https://chromium-review.googlesource.com/1175912Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55147}

src/compiler/js-heap-broker.cc

@@ -277,8 +277,16 @@ JSHeapBroker::JSHeapBroker(Isolate* isolate, Zone* zone)
       zone_(zone),
       refs_(zone),
       mode_(FLAG_concurrent_compiler_frontend ? kSerializing : kDisabled) {
+  Trace("%s", "Constructing heap broker.\n");
+}
+
+void JSHeapBroker::Trace(const char* format, ...) const {
   if (FLAG_trace_heap_broker) {
-    PrintF("[%p] Constructing heap broker.\n", this);
+    PrintF("[%p] ", this);
+    va_list arguments;
+    va_start(arguments, format);
+    base::OS::VPrint(format, arguments);
+    va_end(arguments);
   }
 }
 
@@ -288,9 +296,7 @@ bool JSHeapBroker::SerializingAllowed() const {
 }
 
 void JSHeapBroker::SerializeStandardObjects() {
-  if (FLAG_trace_heap_broker) {
-    PrintF("[%p] Serializing standard objects.\n", this);
-  }
+  Trace("Serializing standard objects.\n");
 
   Builtins* const b = isolate()->builtins();
   Factory* const f = isolate()->factory();
@@ -392,9 +398,8 @@ ObjectData* JSHeapBroker::GetOrCreateData(Handle<Object> object) {
 }
 
 void JSHeapBroker::AddData(Handle<Object> object, ObjectData* data) {
+  Trace("Creating data %p for handle %" V8PRIuPTR " (", data, object.address());
   if (FLAG_trace_heap_broker) {
-    PrintF("[%p] Creating data %p for handle %" V8PRIuPTR " (", this, data,
-           object.address());
     object->ShortPrint();
     PrintF(")\n");
   }

src/compiler/js-heap-broker.h

@@ -428,6 +428,8 @@ class V8_EXPORT_PRIVATE JSHeapBroker : public NON_EXPORTED_BASE(ZoneObject) {
   ObjectData* GetOrCreateData(Handle<Object>);
   void AddData(Handle<Object> object, ObjectData* data);
 
+  void Trace(const char* format, ...) const;
+
  private:
   friend class HeapObjectRef;
   friend class ObjectRef;