Reset GC timings after SIGQUIT.

We now reset the GC timings when a SIGQUIT happens, this is useful
for excluding GCs which happen during the initialization of an app
when measuring GC performance.

Change-Id: I68c79bdb279290c12ae588bc7e95ac24908c157e
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index e3fa834..feb7a48 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -660,7 +660,7 @@
 
   // Dump cumulative loggers for each GC type.
   uint64_t total_paused_time = 0;
-  for (const auto& collector : garbage_collectors_) {
+  for (auto& collector : garbage_collectors_) {
     const CumulativeLogger& logger = collector->GetCumulativeTimings();
     if (logger.GetTotalNs() != 0) {
       os << ConstDumpable<CumulativeLogger>(logger);
@@ -680,6 +680,7 @@
       total_duration += total_ns;
       total_paused_time += total_pause_ns;
     }
+    collector->ResetMeasurements();
   }
   uint64_t allocation_time = static_cast<uint64_t>(total_allocation_time_) * kTimeAdjust;
   if (total_duration != 0) {