metrics: Make it easy to analyze the gzipped protobufs field trial.

* Create the field trial at initialization time, so it gets included in
the first upload.
* Use one-time-randomization to select the experimental group.

BUG=none
TEST=git cl try. Also built locally and ran it successfully.

Review URL: https://chromiumcodereview.appspot.com/18615013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210914 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 83 insertions, 46 deletions

diff --git a/chrome/browser/chrome_browser_field_trials.cc b/chrome/browser/chrome_browser_field_trials.cc
index 00256c7..aae3171 100644
--- a/chrome/browser/chrome_browser_field_trials.cc
+++ b/chrome/browser/chrome_browser_field_trials.cc
@@ -11,6 +11,7 @@
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
+#include "chrome/browser/metrics/gzipped_protobufs_field_trial.h"
 #include "chrome/browser/omnibox/omnibox_field_trial.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/chrome_version_info.h"
@@ -38,6 +39,7 @@ void ChromeBrowserFieldTrials::SetupFieldTrials(PrefService* local_state) {
 
   // Field trials that are shared by all platforms.
   chrome_variations::SetupUniformityFieldTrials(install_time);
+  metrics::CreateGzippedProtobufsFieldTrial();
   InstantiateDynamicTrials();
 
 #if defined(OS_ANDROID) || defined(OS_IOS)
diff --git a/chrome/browser/metrics/gzipped_protobufs_field_trial.cc b/chrome/browser/metrics/gzipped_protobufs_field_trial.cc
new file mode 100644
index 0000000..e12290d
--- /dev/null
+++ b/chrome/browser/metrics/gzipped_protobufs_field_trial.cc
@@ -0,0 +1,55 @@
+// Copyright 2013 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 "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
+
+namespace {
+
+// Name of field trial for that sends gzipped UMA protobufs.
+const char kTrialName[] = "GZippedProtobufs";
+
+// Divisor for the gzipped protobufs trial.
+const int kTrialDivisor = 100;
+
+// Quotient for the gzipped protobufs trial.
+const int kTrialQuotient = 50;
+
+// Name of the group with gzipped protobufs.
+const char kGroupName[] = "GzippedProtobufsEnabled";
+
+// Name of the group with non-gzipped protobufs.
+const char kControlGroupName[] = "GzippedProtobufsDisabled";
+
+// This is set to true if we land in the Finch group that will be sending
+// protobufs after compressing them.
+bool should_gzip_protobufs = false;
+
+}  // namespace
+
+namespace metrics {
+
+void CreateGzippedProtobufsFieldTrial() {
+  scoped_refptr<base::FieldTrial> gzipped_protobufs_trial =
+      base::FieldTrialList::FactoryGetFieldTrial(
+          kTrialName,
+          kTrialDivisor,
+          kControlGroupName,
+          2013,
+          9,
+          1,
+          NULL);
+  gzipped_protobufs_trial->UseOneTimeRandomization();
+  int gzipped_protobufs_group = gzipped_protobufs_trial->AppendGroup(
+      kGroupName,
+      kTrialQuotient);
+  should_gzip_protobufs =
+      gzipped_protobufs_trial->group() == gzipped_protobufs_group;
+}
+
+bool ShouldGzipProtobufsBeforeUploading() {
+  return should_gzip_protobufs;
+}
+
+}  // namespace metrics
diff --git a/chrome/browser/metrics/gzipped_protobufs_field_trial.h b/chrome/browser/metrics/gzipped_protobufs_field_trial.h
new file mode 100644
index 0000000..fe39f01
--- /dev/null
+++ b/chrome/browser/metrics/gzipped_protobufs_field_trial.h
@@ -0,0 +1,21 @@
+// Copyright 2013 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.
+
+#ifndef CHROME_BROWSER_METRICS_GZIPPED_PROTOBUFS_FIELD_TRIAL_H_
+#define CHROME_BROWSER_METRICS_GZIPPED_PROTOBUFS_FIELD_TRIAL_H_
+
+namespace metrics {
+
+// Create a field trial for selecting whether to gzip protobufs before uploading
+// or not.
+void CreateGzippedProtobufsFieldTrial();
+
+// Returns whether we are in a field trial group that compresses protobufs
+// before uploading.
+bool ShouldGzipProtobufsBeforeUploading();
+
+}  // namespace metrics
+
+
+#endif  // CHROME_BROWSER_METRICS_GZIPPED_PROTOBUFS_FIELD_TRIAL_H_
diff --git a/chrome/browser/metrics/metrics_service.cc b/chrome/browser/metrics/metrics_service.cc
index 752cf83..784c615 100644
--- a/chrome/browser/metrics/metrics_service.cc
+++ b/chrome/browser/metrics/metrics_service.cc
@@ -176,6 +176,7 @@
 #include "chrome/browser/io_thread.h"
 #include "chrome/browser/memory_details.h"
 #include "chrome/browser/metrics/compression_utils.h"
+#include "chrome/browser/metrics/gzipped_protobufs_field_trial.h"
 #include "chrome/browser/metrics/metrics_log.h"
 #include "chrome/browser/metrics/metrics_log_serializer.h"
 #include "chrome/browser/metrics/metrics_reporting_scheduler.h"
@@ -271,21 +272,6 @@ const size_t kUploadLogAvoidRetransmitSize = 50000;
 // Interval, in minutes, between state saves.
 const int kSaveStateIntervalMinutes = 5;
 
-// Name of field trial for that sends gzipped UMA protobufs.
-const char kGzippedProtobufsTrialName[] = "GZippedProtobufs";
-
-// Divisor for the gzipped protobufs trial.
-const int kGzippedProtobufsTrialDivisor = 100;
-
-// Quotient for the gzipped protobufs trial.
-const int kGzippedProtobufsTrialQuotient = 50;
-
-// Name of the group with gzipped protobufs.
-const char kGzippedProtobufsGroupName[] = "GzippedProtobufsEnabled";
-
-// Name of the group with non-gzipped protobufs.
-const char kNonGzippedProtobufsGroupName[] = "GzippedProtobufsDisabled";
-
 enum ResponseStatus {
   UNKNOWN_FAILURE,
   SUCCESS,
@@ -486,7 +472,6 @@ MetricsService::MetricsService()
       reporting_active_(false),
       test_mode_active_(false),
       state_(INITIALIZED),
-      gzipped_protobufs_group_(0),
       low_entropy_source_(kLowEntropySourceNotSet),
       idle_since_last_transmission_(false),
       next_window_id_(0),
@@ -1438,7 +1423,8 @@ void MetricsService::PrepareFetchWithStagedLog() {
     // Compress the protobufs 50% of the time. This can be used to see if
     // compressed protobufs are being mishandled by machines between the
     // client/server or monitoring programs/firewalls on the client.
-    bool gzip_protobuf_before_uploading = GzipProtobufsBeforeUploading();
+    bool gzip_protobuf_before_uploading =
+        metrics::ShouldGzipProtobufsBeforeUploading();
     if (gzip_protobuf_before_uploading) {
       std::string log_text = log_manager_.staged_log_text();
       std::string compressed_log_text;
@@ -1871,23 +1857,6 @@ void MetricsService::StartExternalMetrics() {
 }
 #endif
 
-bool MetricsService::GzipProtobufsBeforeUploading() {
-  if (!gzipped_protobufs_trial_) {
-    gzipped_protobufs_trial_ = base::FieldTrialList::FactoryGetFieldTrial(
-        kGzippedProtobufsTrialName,
-        kGzippedProtobufsTrialDivisor,
-        kNonGzippedProtobufsGroupName,
-        2013,
-        8,
-        1,
-        NULL);
-    gzipped_protobufs_group_ = gzipped_protobufs_trial_->AppendGroup(
-        kGzippedProtobufsGroupName,
-        kGzippedProtobufsTrialQuotient);
-  }
-  return gzipped_protobufs_trial_->group() == gzipped_protobufs_group_;
-}
-
 // static
 bool MetricsServiceHelper::IsMetricsReportingEnabled() {
   bool result = false;
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index ced1614..52c9152 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -405,10 +405,6 @@ class MetricsService
   // process, and false otherwise.
   static bool IsPluginProcess(int process_type);
 
-  // Returns true if we are in the Finch experiment group that should compress
-  // protobufs before uploading.
-  bool GzipProtobufsBeforeUploading();
-
   content::ActionCallback action_callback_;
 
   content::NotificationRegistrar registrar_;
@@ -439,14 +435,6 @@ class MetricsService
   // Google Update statistics, which were retrieved on a blocking pool thread.
   GoogleUpdateMetrics google_update_metrics_;
 
-  // Field trial that determines whether we gzip protobufs before uploading
-  // them.
-  scoped_refptr<base::FieldTrial> gzipped_protobufs_trial_;
-
-  // The integer value corresponding to the group that will be gzipping
-  // protobufs before uploading them.
-  int gzipped_protobufs_group_;
-
   // The initial log, used to record startup metrics.
   scoped_ptr<MetricsLog> initial_log_;
 
diff --git a/chrome/chrome_browser.gypi b/chrome/chrome_browser.gypi
index bf9ebd3..2f01cb1 100644
--- a/chrome/chrome_browser.gypi
+++ b/chrome/chrome_browser.gypi
@@ -1059,6 +1059,8 @@
         'browser/metrics/compression_utils.h',
         'browser/metrics/field_trial_synchronizer.cc',
         'browser/metrics/field_trial_synchronizer.h',
+        'browser/metrics/gzipped_protobufs_field_trial.cc',
+        'browser/metrics/gzipped_protobufs_field_trial.h',
         'browser/metrics/metric_event_duration_details.h',
         'browser/metrics/metrics_log.cc',
         'browser/metrics/metrics_log.h',