[heap] Print memory mode in --trace-gc-nvp.

src/heap/gc-tracer.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_TRACER_H_
 #define V8_HEAP_GC_TRACER_H_
 
 #include "src/base/platform/platform.h"
 #include "src/globals.h"
 
@@ skipping 200 matching lines @@
 
     const char* gc_reason;
     const char* collector_reason;
 
     // Timestamp set in the constructor.
     double start_time;
 
     // Timestamp set in the destructor.
     double end_time;
 
+    // Memory reduction flag set.
+    bool reduce_memory;
+
     // Size of objects in heap set in constructor.
     intptr_t start_object_size;
 
     // Size of objects in heap set in destructor.
     intptr_t end_object_size;
 
     // Size of memory allocated from OS set in constructor.
     intptr_t start_memory_size;
 
     // Size of memory allocated from OS set in destructor.
@@ skipping 321 matching lines @@
 
   // Counts how many tracers were started without stopping.
   int start_counter_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_GC_TRACER_H_