Add more fine grained UMA for ExtensionService initialization time. At the

moment there is only total time and time to load all non-component extensions.
Time to load component extensions and time to notify all listeners is not
instrumented.

R=mek@chromium.org, mpearson@chromium.org
BUG=453073

Review URL: https://codereview.chromium.org/883023003

Cr-Commit-Position: refs/heads/master@{#313615}

chrome/browser/extensions/component_loader.cc

@@ -10,7 +10,9 @@
 #include "base/files/file_util.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/metrics/field_trial.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/path_service.h"
+#include "base/time/time.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/search/hotword_service.h"
 #include "chrome/browser/search/hotword_service_factory.h"
@@ -124,11 +126,14 @@ ComponentLoader::~ComponentLoader() {
 }
 
 void ComponentLoader::LoadAll() {
+  const base::TimeTicks start_time = base::TimeTicks::Now();
   for (RegisteredComponentExtensions::iterator it =
           component_extensions_.begin();
       it != component_extensions_.end(); ++it) {
     Load(*it);
   }
+  UMA_HISTOGRAM_TIMES("Extensions.LoadAllComponentTime",
+                      base::TimeTicks::Now() - start_time);
 }
 
 base::DictionaryValue* ComponentLoader::ParseManifest(

chrome/browser/extensions/extension_service.cc

@@ -1410,11 +1410,14 @@ void ExtensionService::ReloadExtensionsForTest() {
 }
 
 void ExtensionService::SetReadyAndNotifyListeners() {
+  const base::TimeTicks start_time = base::TimeTicks::Now();
   ready_->Signal();
   content::NotificationService::current()->Notify(
       extensions::NOTIFICATION_EXTENSIONS_READY_DEPRECATED,
       content::Source<Profile>(profile_),
       content::NotificationService::NoDetails());
+  UMA_HISTOGRAM_TIMES("Extensions.ExtensionServiceNotifyReadyListenersTime",
+                      base::TimeTicks::Now() - start_time);
 }
 
 void ExtensionService::OnLoadedInstalledExtensions() {

tools/metrics/histograms/histograms.xml

@@ -8144,6 +8144,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.ExtensionServiceNotifyReadyListenersTime">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    Time taken for the ExtensionService to notify all ready listeners that the
+    extension system is now ready. This happens as part of the total
+    initialization time of ExtensionService, measured in
+    Extensions.ExtensionServiceInitTime.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.ExtensionUninstalled">
   <owner>kalman@chromium.org</owner>
   <summary>An extension has been uninstalled.</summary>
@@ -8405,9 +8415,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Extensions.LoadAllComponentTime" units="milliseconds">
+  <owner>kalman@chromium.org</owner>
+  <summary>
+    Time taken to load all component extensions at browser startup. This happens
+    as part of the total initialization time of ExtensionService, measured in
+    Extensions.ExtensionServiceInitTime.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.LoadAllTime" units="milliseconds">
   <owner>kalman@chromium.org</owner>
-  <summary>Time taken to load all extensions at browser startup.</summary>
+  <summary>
+    Time taken to load all non-component extensions at browser startup. This
+    happens as part of the total initialization time of ExtensionService,
+    measured in Extensions.ExtensionServiceInitTime.
+  </summary>
 </histogram>
 
 <histogram name="Extensions.LoadApp">