Record start up latency of DOM distiller viewer

components/dom_distiller/content/browser/dom_distiller_viewer_source.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/dom_distiller/content/browser/dom_distiller_viewer_source.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop.h"
-#include "base/metrics/user_metrics.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/dom_distiller/content/browser/distiller_javascript_service_impl.h"
 #include "components/dom_distiller/content/browser/distiller_javascript_utils.h"
 #include "components/dom_distiller/content/browser/distiller_ui_handle.h"
 #include "components/dom_distiller/content/common/distiller_page_notifier_service.mojom.h"
 #include "components/dom_distiller/core/distilled_page_prefs.h"
 #include "components/dom_distiller/core/dom_distiller_request_view_base.h"
 #include "components/dom_distiller/core/dom_distiller_service.h"
@@ skipping 125 matching lines @@
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }
 
 void DomDistillerViewerSource::RequestViewerHandle::DidFinishLoad(
     content::RenderFrameHost* render_frame_host,
     const GURL& validated_url) {
   if (render_frame_host->GetParent()) {
     return;
   }
 
+  int64_t start_time_ms = url_utils::GetTimeFromDistillerUrl(validated_url);
+  if (start_time_ms > 0) {
+    base::TimeTicks start_time =
+        base::TimeDelta::FromMilliseconds(start_time_ms) + base::TimeTicks();
+    base::TimeDelta latency = base::TimeTicks::Now() - start_time;
+
+    UMA_HISTOGRAM_TIMES("DomDistiller.Time.ViewerLoading", latency);
+  }
+
   // No SendJavaScript() calls allowed before |buffer_| is run and cleared.
   waiting_for_page_ready_ = false;
   if (!buffer_.empty()) {
     RunIsolatedJavaScript(web_contents()->GetMainFrame(), buffer_);
     buffer_.clear();
   }
   // No need to Cancel() here.
 }
 
 DomDistillerViewerSource::DomDistillerViewerSource(
@@ skipping 113 matching lines @@
 std::string DomDistillerViewerSource::GetContentSecurityPolicyObjectSrc()
     const {
   return "object-src 'none'; style-src 'self' https://fonts.googleapis.com;";
 }
 
 std::string DomDistillerViewerSource::GetContentSecurityPolicyFrameSrc() const {
   return "frame-src *;";
 }
 
 }  // namespace dom_distiller