This defers starting background extension page RenderViews

chrome/browser/profiles/profile_manager.cc

Index: chrome/browser/profiles/profile_manager.cc
diff --git a/chrome/browser/profiles/profile_manager.cc b/chrome/browser/profiles/profile_manager.cc
index ec088d2d43008e0422e27d3454ade176688904b9..48f3c0962b734112e58117fab46b650b5a7409a9 100644
--- a/chrome/browser/profiles/profile_manager.cc
+++ b/chrome/browser/profiles/profile_manager.cc
@@ -13,6 +13,7 @@
 #include "base/file_util.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_number_conversions.h"
@@ -733,8 +734,37 @@ void ProfileManager::DoFinalInit(Profile* profile, bool go_off_the_record) {
 void ProfileManager::DoFinalInitForServices(Profile* profile,
                                             bool go_off_the_record) {
 #if defined(ENABLE_EXTENSIONS)
+  // Set up a field trial to determine the effectiveness of deferring
+  // creation of background extension RenderViews.
+  CR_DEFINE_STATIC_LOCAL(scoped_refptr<base::FieldTrial>, trial, ());
+  static bool defer_creation = false;
+
+  if (!trial.get()) {
+    const base::FieldTrial::Probability kDivisor = 100;
+
+    // Enable the deferred creation for 50% of the users.
+    base::FieldTrial::Probability probability_per_group = 50;
+
+    // After August 31, 2014 builds, it will always be in default group
+    // (defer_creation == false).
+    trial = base::FieldTrialList::FactoryGetFieldTrial(
+        "DeferBackgoundExtensionCreation",

[Miranda Callahan, 2013/09/05 12:02:03]

nit: s/ackgo/ackgro

[Greg Spencer (Chromium), 2013/09/05 18:33:25]

Done.

+        kDivisor,
+        "RateLimited",
+        2014,
+        8,
+        31,
+        base::FieldTrial::ONE_TIME_RANDOMIZED,
+        NULL);
+
+    // Add group for deferred creation of background extension RenderViews.
+    int defer_creation_group =
+        trial->AppendGroup("Deferred", probability_per_group);
+    defer_creation = trial->group() == defer_creation_group;
+  }
+
   extensions::ExtensionSystem::Get(profile)->InitForRegularProfile(
-      !go_off_the_record);
+      !go_off_the_record, defer_creation);
   // During tests, when |profile| is an instance of TestingProfile,
   // ExtensionSystem might not create an ExtensionService.
   if (extensions::ExtensionSystem::Get(profile)->extension_service()) {