[Media Router] Add UMA metrics for Media Router Dialog WebUI performance.

chrome/browser/ui/webui/media_router/media_router_webui_message_handler.cc

 // Copyright 2015 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 "chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
@@ skipping 11 matching lines @@
 const char kHelpPageUrlPrefix[] =
     "https://support.google.com/chromecast/answer/%d";
 
 // Message names.
 const char kRequestInitialData[] = "requestInitialData";
 const char kCreateRoute[] = "requestRoute";
 const char kActOnIssue[] = "actOnIssue";
 const char kCloseRoute[] = "closeRoute";
 const char kCloseDialog[] = "closeDialog";
 const char kReportSinkCount[] = "reportSinkCount";
+const char kOnInitialDataReceived[] = "onInitialDataReceived";
 
 // JS function names.
 const char kSetInitialData[] = "media_router.ui.setInitialData";
 const char kNotifyRouteCreationTimeout[] =
     "media_router.ui.onNotifyRouteCreationTimeout";
 const char kOnCreateRouteResponseReceived[] =
     "media_router.ui.onCreateRouteResponseReceived";
 const char kSetIssue[] = "media_router.ui.setIssue";
 const char kSetSinkList[] = "media_router.ui.setSinkList";
 const char kSetRouteList[] = "media_router.ui.setRouteList";
@@ skipping 207 matching lines @@
       base::Bind(&MediaRouterWebUIMessageHandler::OnCloseRoute,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       kCloseDialog,
       base::Bind(&MediaRouterWebUIMessageHandler::OnCloseDialog,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       kReportSinkCount,
       base::Bind(&MediaRouterWebUIMessageHandler::OnReportSinkCount,
                  base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      kOnInitialDataReceived,
+      base::Bind(&MediaRouterWebUIMessageHandler::OnInitialDataReceived,
+                 base::Unretained(this)));
 }
 
 void MediaRouterWebUIMessageHandler::OnRequestInitialData(
     const base::ListValue* args) {
   DVLOG(1) << "OnRequestInitialData";
+  media_router_ui_->OnUIInitiallyLoaded();

[mark a. foltz, 2015/12/09 22:20:13]

When is this called in the initialization flow?  It seems like we are capturing
some script execution time as well.  Does this happen after the top level
Polymer elements have been created for the default view?

[apacible, 2015/12/09 23:19:55]

This is called ASAP when the WebUI finishes loading.

The flow looks like:
1. User action to open dialog.
2. Dialog created (not shown yet).
3. WebUI page loads ('load' event fired).
4. 'load' event triggers initialize().
5. initialize() immediately calls requestInitialData()
6. requestInitialData() immediately calls OnRequestInitialData() here.
7. OnRequestInitialData() immediately calls OnUIInitiallyLoaded(). <- log here

I previously added some logging to look at initialization flow (not included in
the CL since it was just for sanity checks) and the page loading includes the
creation of the Polymer elements.

   base::DictionaryValue initial_data;
 
   // "No Cast devices found?" Chromecast help center page.
   initial_data.SetString("deviceMissingUrl",
       base::StringPrintf(kHelpPageUrlPrefix, 3249268));
 
   scoped_ptr<base::ListValue> sinks(SinksToValue(media_router_ui_->sinks()));
   initial_data.Set("sinks", sinks.release());
 
   scoped_ptr<base::ListValue> routes(RoutesToValue(media_router_ui_->routes(),
@@ skipping 114 matching lines @@
     const base::ListValue* args) {
   DVLOG(1) << "OnReportSinkCount";
   int sink_count;
   if (!args->GetInteger(0, &sink_count)) {
     DVLOG(1) << "Unable to extract args.";
     return;
   }
   UMA_HISTOGRAM_COUNTS_100("MediaRouter.Ui.Device.Count", sink_count);
 }
 
+void MediaRouterWebUIMessageHandler::OnInitialDataReceived(
+    const base::ListValue* args) {
+  DVLOG(1) << "OnInitialDataReceived";
+  media_router_ui_->OnUIInitialDataReceived();
+}
+
 bool MediaRouterWebUIMessageHandler::ActOnIssueType(
     const IssueAction::Type& action_type,
     const base::DictionaryValue* args) {
   if (action_type == IssueAction::TYPE_LEARN_MORE) {
     std::string learn_more_url = GetLearnMoreUrl(args);
     if (learn_more_url.empty())
       return false;
     scoped_ptr<base::ListValue> open_args(new base::ListValue);
     open_args->AppendString(learn_more_url);
     web_ui()->CallJavascriptFunction(kWindowOpen, *open_args);
     return true;
   } else {
     // Do nothing; no other issue action types require any other action.
     return true;
   }
 }
 
 }  // namespace media_router