Uncommit and shrink semi-spaces only on low allocation rate.

src/heap/gc-idle-time-handler.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_GC_IDLE_TIME_HANDLER_H_
 #define V8_HEAP_GC_IDLE_TIME_HANDLER_H_
 
 #include "src/globals.h"
 
 namespace v8 {
@@ skipping 170 matching lines @@
     bool can_start_incremental_marking;
     bool sweeping_in_progress;
     bool sweeping_completed;
     size_t mark_compact_speed_in_bytes_per_ms;
     size_t incremental_marking_speed_in_bytes_per_ms;
     size_t final_incremental_mark_compact_speed_in_bytes_per_ms;
     size_t scavenge_speed_in_bytes_per_ms;
     size_t used_new_space_size;
     size_t new_space_capacity;
     size_t new_space_allocation_throughput_in_bytes_per_ms;
+    size_t current_new_space_allocation_throughput_in_bytes_per_ms;
   };
 
   GCIdleTimeHandler()
       : idle_mark_compacts_(0),
         mark_compacts_(0),
         scavenges_(0),
         long_idle_notifications_(0),
         background_idle_notifications_(0),
         idle_times_which_made_no_progress_per_mode_(0),
         next_gc_likely_to_collect_more_(false),
@@ skipping 68 matching lines @@
 
   Mode mode_;
 
   DISALLOW_COPY_AND_ASSIGN(GCIdleTimeHandler);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_GC_IDLE_TIME_HANDLER_H_