Print PID and isolate address in gc traces.

src/heap/gc-tracer.cc

Index: src/heap/gc-tracer.cc
diff --git a/src/heap/gc-tracer.cc b/src/heap/gc-tracer.cc
index 6f3a03f98b3525b4b9ae00af361489125a4f35a7..f545b2f134f275811110709f123a6cc7a1efdb6b 100644
--- a/src/heap/gc-tracer.cc
+++ b/src/heap/gc-tracer.cc
@@ -276,7 +276,8 @@ void GCTracer::AddIncrementalMarkingStep(double duration, intptr_t bytes) {
 
 
 void GCTracer::Print() const {
-  PrintPID("%8.0f ms: ", heap_->isolate()->time_millis_since_init());
+  PrintIsolate(heap_->isolate(), "%8.0f ms: ",
+               heap_->isolate()->time_millis_since_init());
 
   PrintF("%s %.1f (%.1f) -> %.1f (%.1f) MB, ", current_.TypeName(false),
          static_cast<double>(current_.start_object_size) / MB,
@@ -319,7 +320,8 @@ void GCTracer::Print() const {
 
 
 void GCTracer::PrintNVP() const {
-  PrintPID("%8.0f ms: ", heap_->isolate()->time_millis_since_init());
+  PrintIsolate(heap_->isolate(), "[I:%p] %8.0f ms: ", heap_->isolate(),
+               heap_->isolate()->time_millis_since_init());
 
   double duration = current_.end_time - current_.start_time;
   double spent_in_mutator = current_.start_time - previous_.end_time;