[heap] Add GCTracer scope for rebalancing new space

BUG=

Change-Id: I7215f298d7da4f5104449cc9198588801642bba1
Reviewed-on: https://chromium-review.googlesource.com/443126Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43223}

src/heap/gc-tracer.cc

@@ -541,6 +541,7 @@ void GCTracer::PrintNVP() const {
           "evacuate.candidates=%.1f "
           "evacuate.clean_up=%.1f "
           "evacuate.copy=%.1f "
+          "evacuate.rebalance=%.1f "
           "evacuate.update_pointers=%.1f "
           "evacuate.update_pointers.to_evacuated=%.1f "
           "evacuate.update_pointers.to_new=%.1f "
@@ -624,6 +625,7 @@ void GCTracer::PrintNVP() const {
           current_.scopes[Scope::MC_EVACUATE_CANDIDATES],
           current_.scopes[Scope::MC_EVACUATE_CLEAN_UP],
           current_.scopes[Scope::MC_EVACUATE_COPY],
+          current_.scopes[Scope::MC_EVACUATE_REBALANCE],
           current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS],
           current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_TO_EVACUATED],
           current_.scopes[Scope::MC_EVACUATE_UPDATE_POINTERS_TO_NEW],

src/heap/gc-tracer.h

@@ -56,6 +56,7 @@ enum ScavengeSpeedMode { kForAllObjects, kForSurvivedObjects };
   F(MC_EVACUATE_CANDIDATES)                   \
   F(MC_EVACUATE_CLEAN_UP)                     \
   F(MC_EVACUATE_COPY)                         \
+  F(MC_EVACUATE_REBALANCE)                    \
   F(MC_EVACUATE_UPDATE_POINTERS)              \
   F(MC_EVACUATE_UPDATE_POINTERS_TO_EVACUATED) \
   F(MC_EVACUATE_UPDATE_POINTERS_TO_NEW)       \

src/heap/mark-compact.cc

@@ -3562,8 +3562,11 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
 
   UpdatePointersAfterEvacuation();
 
-  if (!heap()->new_space()->Rebalance()) {
-    FatalProcessOutOfMemory("NewSpace::Rebalance");
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_EVACUATE_REBALANCE);
+    if (!heap()->new_space()->Rebalance()) {
+      FatalProcessOutOfMemory("NewSpace::Rebalance");
+    }
   }
 
   // Give pages that are queued to be freed back to the OS. Note that filtering