[heap] Add GCTracer for updating refs after scavenge

Updating refs to new space in internal data structures could take some
time, so also measure this.

Bug: chromium:844008
Change-Id: I9f5af4d09f8ef580ca0ad0019cfc78a994d62ffd
Reviewed-on: https://chromium-review.googlesource.com/1128889Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@google.com>
Cr-Commit-Position: refs/heads/master@{#54328}

src/heap-symbols.h

@@ -375,6 +375,7 @@
   F(SCAVENGER_SCAVENGE_WEAK_GLOBAL_HANDLES_PROCESS)  \
   F(SCAVENGER_SCAVENGE_PARALLEL)                     \
   F(SCAVENGER_SCAVENGE_ROOTS)                        \
+  F(SCAVENGER_SCAVENGE_UPDATE_REFS)                  \
   F(SCAVENGER_SCAVENGE_WEAK)
 
 #define TRACER_BACKGROUND_SCOPES(F)               \

src/heap/gc-tracer.cc

@@ -532,6 +532,7 @@ void GCTracer::PrintNVP() const {
           "scavenge.weak_global_handles.identify=%.2f "
           "scavenge.weak_global_handles.process=%.2f "
           "scavenge.parallel=%.2f "
+          "scavenge.update_refs=%.2f "
           "background.scavenge.parallel=%.2f "
           "background.array_buffer_free=%.2f "
           "background.store_buffer=%.2f "
@@ -580,6 +581,7 @@ void GCTracer::PrintNVP() const {
           current_
               .scopes[Scope::SCAVENGER_SCAVENGE_WEAK_GLOBAL_HANDLES_PROCESS],
           current_.scopes[Scope::SCAVENGER_SCAVENGE_PARALLEL],
+          current_.scopes[Scope::SCAVENGER_SCAVENGE_UPDATE_REFS],
           current_.scopes[Scope::SCAVENGER_BACKGROUND_SCAVENGE_PARALLEL],
           current_.scopes[Scope::BACKGROUND_ARRAY_BUFFER_FREE],
           current_.scopes[Scope::BACKGROUND_STORE_BUFFER],

src/heap/heap.cc

@@ -2242,10 +2242,14 @@ void Heap::Scavenge() {
     }
   }
 
-  UpdateNewSpaceReferencesInExternalStringTable(
-      &UpdateNewSpaceReferenceInExternalStringTableEntry);
+  {
+    // Update references into new space
+    TRACE_GC(tracer(), GCTracer::Scope::SCAVENGER_SCAVENGE_UPDATE_REFS);
+    UpdateNewSpaceReferencesInExternalStringTable(
+        &UpdateNewSpaceReferenceInExternalStringTableEntry);
 
-  incremental_marking()->UpdateMarkingWorklistAfterScavenge();
+    incremental_marking()->UpdateMarkingWorklistAfterScavenge();
+  }
 
   if (FLAG_concurrent_marking) {
     // Ensure that concurrent marker does not track pages that are