Stability instrumentation: metrics for collection on crash

components/browser_watcher/stability_report_user_stream_data_source.cc

Index: components/browser_watcher/stability_report_user_stream_data_source.cc
diff --git a/components/browser_watcher/stability_report_user_stream_data_source.cc b/components/browser_watcher/stability_report_user_stream_data_source.cc
index 62fdf2235edd63531b4c6d53b8985b846af9632d..928e7eb91419c90e0bdc2847327f1b9b5a0b77d0 100644
--- a/components/browser_watcher/stability_report_user_stream_data_source.cc
+++ b/components/browser_watcher/stability_report_user_stream_data_source.cc
@@ -73,6 +73,8 @@ bool BufferExtensionStreamDataSource::ReadStreamData(Delegate* delegate) {
       data_.size() ? data_.data() : nullptr, data_.size());
 }
 
+// TODO(manzagop): collection should factor in whether this is a true crash or
+// dump without crashing.
 std::unique_ptr<BufferExtensionStreamDataSource> CollectReport(
     const base::FilePath& path) {
   StabilityReport report;
@@ -91,6 +93,8 @@ std::unique_ptr<BufferExtensionStreamDataSource> CollectReport(
                             base::File::FLAG_DELETE_ON_CLOSE);
   UMA_HISTOGRAM_BOOLEAN("ActivityTracker.CollectCrash.OpenForDeleteSuccess",
                         file.IsValid());
+  UMA_STABILITY_HISTOGRAM_COUNTS_100("ActivityTracker.CollectCrash.CrashCount",

[Sigurður Ásgeirsson, 2017/05/30 13:46:37]

QQ: is this the best way to record this? I've seen enums used to record event
counts before. They're not super-convenient to decipher, but have the advantage
of being extensible to new events and presumably fairly dense in memory and on
wire.

[manzagop (departed), 2017/05/30 16:16:54]

I'd want the metric to be usable in a timeline formula for coverage estimation.
Is that possible?

+                                     1);
 
   std::unique_ptr<BufferExtensionStreamDataSource> source(
       new BufferExtensionStreamDataSource(kStabilityReportStreamType));