Fix incorrect accumulation count.

The previous count was increment every time the result was negative
which meant it was counted many times since a negative count is likely
to remain negative for some time.

Also add some new histograms that are overflowing to the enum.

Bug: 682680
Change-Id: Ib7c7c5040c6a507e3b125280e975db4bff37a56b
Reviewed-on: https://chromium-review.googlesource.com/718977
Commit-Queue: Brian White <bcwhite@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508798}

base/metrics/persistent_sample_map.cc

@@ -26,6 +26,7 @@ enum NegativeSampleReason {
   PERSISTENT_SPARSE_ADD_OVERFLOW,
   PERSISTENT_SPARSE_ACCUMULATE_NEGATIVE_COUNT,
   PERSISTENT_SPARSE_ACCUMULATE_WENT_NEGATIVE,
+  DEPRECATED_PERSISTENT_SPARSE_ACCUMULATE_OVERFLOW,
   PERSISTENT_SPARSE_ACCUMULATE_OVERFLOW,
   MAX_NEGATIVE_SAMPLE_REASONS
 };
@@ -132,8 +133,10 @@ void PersistentSampleMap::Accumulate(Sample value, Count count) {
       reason = PERSISTENT_SPARSE_ACCUMULATE_WENT_NEGATIVE;
     *local_count_ptr += count;
   } else {
-    *local_count_ptr += count;
-    if (*local_count_ptr < 0)
+    Sample old_value = *local_count_ptr;
+    Sample new_value = old_value + count;
+    *local_count_ptr = new_value;
+    if ((new_value >= 0) != (old_value >= 0))
       reason = PERSISTENT_SPARSE_ACCUMULATE_OVERFLOW;
   }
   if (reason != MAX_NEGATIVE_SAMPLE_REASONS) {

tools/metrics/histograms/enums.xml

@@ -19792,6 +19792,8 @@ uploading your change for review.  These are checked by presubmit scripts.
   <int value="-2055973512" label="Login.ConsumerNewUsersAllowed"/>
   <int value="-2021219906"
       label="DataUse.MessageSize.AllServices.Downstream.Foreground.NotCellular"/>
+  <int value="-1724216561"
+      label="Extensions.Functions.SucceededTime.LessThan1ms"/>
   <int value="-1620411628"
       label="DataUse.MessageSize.AllServices.Downstream.Unknown.NotCellular"/>
   <int value="-1607339868"
@@ -19818,6 +19820,7 @@ uploading your change for review.  These are checked by presubmit scripts.
       label="DataUse.MessageSize.AllServices.Downstream.Unknown.Cellular"/>
   <int value="424952287"
       label="Network.Shill.Wifi.LinkMonitorResponseTimeSample"/>
+  <int value="433324211" label="Extensions.FunctionCalls"/>
   <int value="628921860"
       label="Network.Shill.Ethernet.LinkMonitorResponseTimeSample"/>
   <int value="662206917"
@@ -19826,6 +19829,7 @@ uploading your change for review.  These are checked by presubmit scripts.
       label="DataUse.MessageSize.AllServices.Upstream.Foreground.Cellular"/>
   <int value="1370064090"
       label="DataUse.MessageSize.AllServices.Upstream.Background.Cellular"/>
+  <int value="1514844119" label="DataUse.Sync.Upload.Bytes"/>
   <int value="1753226325"
       label="DataUse.MessageSize.AllServices.Downstream.Foreground.Cellular"/>
   <int value="1977321258"
@@ -27152,8 +27156,11 @@ from previous Chrome versions.
       label="Persistent sparse histogram accumulated a negative count that
              caused a negative value."/>
   <int value="7"
-      label="Persistent sparse histogram active sample overflowed during
-             accumulation and became negative."/>
+      label="Persistent sparse histogram active sample was negative after
+             accumulation (deprecated)."/>
+  <int value="8"
+      label="Persistent sparse histogram active sample wrapped 2^31 during
+             accumulation."/>
 </enum>
 
 <enum name="NetCacheState">