Persist setup metrics and have Chrome report them during UMA upload.

base/metrics/statistics_recorder.cc

Index: base/metrics/statistics_recorder.cc
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index 7efe16b10c15596f968a4fcced8ad4ae4d7d9ee4..65a9b18b9b62bc39c9c8b626e6d3df758f386271 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -393,24 +393,24 @@ StatisticsRecorder::StatisticsRecorder() {
 
 // static
 void StatisticsRecorder::ResetForTesting() {
-  if (histograms_) {
-    STLDeleteValues(histograms_);
-    delete histograms_;
-    histograms_= nullptr;
-  }
-  if (ranges_) {
-    for (auto& iter : *ranges_) {
-      STLDeleteElements(iter.second);
-      delete iter.second;
-    }
-    delete ranges_;
-    ranges_ = nullptr;
-  }
+  // This leaks a lot of objects but they've already been annotated for such.
+  // Deleting them isn't possible because there could be other pointers to
+  // them somewhere.
+  delete histograms_;
+  histograms_= nullptr;
+  delete ranges_;
+  ranges_ = nullptr;
   delete callbacks_;
   callbacks_ = nullptr;
 }
 
 // static
+void StatisticsRecorder::ForgetHistogramForTesting(const std::string& name) {
+  if (histograms_)
+    histograms_->erase(HashMetricName(name));
+}
+
+// static
 void StatisticsRecorder::DumpHistogramsToVlog(void* instance) {
   std::string output;
   StatisticsRecorder::WriteGraph(std::string(), &output);