Trace scavenger throughput.

src/heap/gc-tracer.h

Index: src/heap/gc-tracer.h
diff --git a/src/heap/gc-tracer.h b/src/heap/gc-tracer.h
index 14281a4c8d90bcd7988ad58833db47381775b351..fd53d3c31ce7121c49f836e1bcf46546e32d5ac4 100644
--- a/src/heap/gc-tracer.h
+++ b/src/heap/gc-tracer.h
@@ -171,6 +171,9 @@ class GCTracer BASE_EMBEDDED {
     // after the current GC.
     intptr_t end_holes_size;
 
+    // Size of new space objects in constructor.
+    intptr_t new_space_object_size;
+
     // Number of incremental marking steps since creation of tracer.
     // (value at start of event)
     int cumulative_incremental_marking_steps;
@@ -280,10 +283,14 @@ class GCTracer BASE_EMBEDDED {
   // Returns 0 if no incremental marking round has been completed.
   double MaxIncrementalMarkingDuration() const;
 
-  // Compute the average incremental marking speed in bytes/second. Returns 0 if
-  // no events have been recorded.
+  // Compute the average incremental marking speed in bytes/millisecond.
+  // Returns 0 if no events have been recorded.
   intptr_t IncrementalMarkingSpeedInBytesPerMillisecond() const;
 
+  // Compute the average scavenge speed in bytes/millisecond.
+  // Returns 0 if no events have been recorded.
+  intptr_t ScavengeSpeedInBytesPerMillisecond() const;
+
  private:
   // Print one detailed trace line in name=value format.
   // TODO(ernstm): Move to Heap.