Use current time to calculate context disposal rate.

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"
 
 namespace v8 {
@@ skipping 323 matching lines @@
 
   // Compute the max mark-sweep speed in bytes/millisecond.
   // Returns 0 if no events have been recorded.
   intptr_t MarkCompactSpeedInBytesPerMillisecond() const;
 
   // Allocation throughput in the new space in bytes/millisecond.
   // Returns 0 if no events have been recorded.
   intptr_t NewSpaceAllocationThroughputInBytesPerMillisecond() const;
 
   // Computes the context disposal rate in milliseconds. It takes the time
-  // frame of the first and last context disposal event and devides it by the
-  // number of recorded events.
+  // frame of the first recorded context disposal to the current time and
+  // divides it by the number of recorded events.
   // Returns 0 if no events have been recorded.
   double ContextDisposalRateInMilliseconds() const;
 
  private:
   // Print one detailed trace line in name=value format.
   // TODO(ernstm): Move to Heap.
   void PrintNVP() const;
 
   // Print one trace line.
   // TODO(ernstm): Move to Heap.
@@ skipping 62 matching lines @@
   // Holds the new space top pointer recorded at the end of the last garbage
   // collection.
   intptr_t new_space_top_after_gc_;
 
   DISALLOW_COPY_AND_ASSIGN(GCTracer);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_GC_TRACER_H_