[heap] Fix type conversion in gc tracer

R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/1438313002

Cr-Commit-Position: refs/heads/master@{#31970}

src/heap/gc-tracer.cc

@@ -731,7 +731,7 @@ intptr_t GCTracer::ScavengeSpeedInBytesPerMillisecond(
 
 
 intptr_t GCTracer::CompactionSpeedInBytesPerMillisecond() const {
-  if (compaction_events_.size() < kRingBufferMaxSize) return 0.0;
+  if (compaction_events_.size() < kRingBufferMaxSize) return 0;
   intptr_t bytes = 0;
   double durations = 0.0;
   CompactionEventBuffer::const_iterator iter = compaction_events_.begin();