History: Add load-time metric for non-MD and MD History WebUI

chrome/browser/ui/webui/metrics_handler.cc

Index: chrome/browser/ui/webui/metrics_handler.cc
diff --git a/chrome/browser/ui/webui/metrics_handler.cc b/chrome/browser/ui/webui/metrics_handler.cc
index 39ef3287ab9a3d97aa38dce4fe8862980fb3c6b8..f5829fe9fc82396a16d1abcfd6b068075c2399f4 100644
--- a/chrome/browser/ui/webui/metrics_handler.cc
+++ b/chrome/browser/ui/webui/metrics_handler.cc
@@ -34,6 +34,9 @@ void MetricsHandler::RegisterMessages() {
       base::Bind(&MetricsHandler::HandleRecordInHistogram,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
+      "metricsHandler:recordTime",
+      base::Bind(&MetricsHandler::HandleRecordTime, base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
       "metricsHandler:logEventTime",
       base::Bind(&MetricsHandler::HandleLogEventTime, base::Unretained(this)));
 }
@@ -77,6 +80,26 @@ void MetricsHandler::HandleRecordInHistogram(const base::ListValue* args) {
   counter->Add(int_value);
 }
 
+void MetricsHandler::HandleRecordTime(const base::ListValue* args) {
+  std::string histogram_name;
+  double value;
+
+  if (!args->GetString(0, &histogram_name) ||
+      !args->GetDouble(1, &value) ||
+      value < 0) {
+    NOTREACHED();
+    return;
+  }
+
+  base::TimeDelta time_value = base::TimeDelta::FromMilliseconds(value);
+
+  base::HistogramBase* counter = base::LinearHistogram::FactoryTimeGet(
+      histogram_name, base::TimeDelta::FromMilliseconds(1),
+      base::TimeDelta::FromSeconds(10), 50,
+      base::HistogramBase::kUmaTargetedHistogramFlag);
+  counter->AddTime(time_value);

[calamity, 2016/08/03 08:23:23]

Why not just UMA_HISTOGRAM_TIMES?

[tsergeant, 2016/08/03 22:53:56]

Histogram names passed into the macros have to be static -- you can't pass in a
variable. Instead, we have to expand the macro manually, which is also what
happens in HandleRecordInHistogram above.

+}
+
 void MetricsHandler::HandleLogEventTime(const base::ListValue* args) {
   std::string event_name = base::UTF16ToUTF8(ExtractStringValue(args));
   WebContents* tab = web_ui()->GetWebContents();