Add function to register a synthetic trial with the trial hash.

This will be used by Android Chrome to register external
experiments.

BUG=400357

Review URL: https://codereview.chromium.org/440693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287695 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/metrics/chrome_metrics_service_accessor.cc

@@ -8,6 +8,7 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/pref_names.h"
 #include "components/metrics/metrics_service.h"
+#include "components/variations/metrics_util.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/settings/cros_settings.h"
@@ -49,9 +50,18 @@ bool ChromeMetricsServiceAccessor::IsCrashReportingEnabled() {
 
 // static
 bool ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-    const std::string& trial, const std::string& group) {
+    const std::string& trial_name,
+    const std::string& group_name) {
+  return RegisterSyntheticFieldTrialWithNameHash(metrics::HashName(trial_name),
+                                                 group_name);
+}
+
+// static
+bool ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameHash(
+    uint32_t trial_name_hash,
+    const std::string& group_name) {
   return MetricsServiceAccessor::RegisterSyntheticFieldTrial(
       g_browser_process->metrics_service(),
-      trial,
-      group);
+      trial_name_hash,
+      metrics::HashName(group_name));
 }

chrome/browser/metrics/chrome_metrics_service_accessor.h

@@ -5,6 +5,9 @@
 #ifndef CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_ACCESSOR_H_
 
+#include <stdint.h>
+#include <string>
+
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "chrome/browser/metrics/metrics_service_accessor.h"
@@ -46,6 +49,7 @@ class ChromeMetricsServiceAccessor : public MetricsServiceAccessor {
   friend class extensions::MetricsPrivateGetIsCrashReportingEnabledFunction;
   friend class ::FlashDOMHandler;
   friend class system_logs::ChromeInternalLogSource;
+  friend class UmaSessionStats;
 
   FRIEND_TEST_ALL_PREFIXES(ChromeMetricsServiceAccessorTest,
                            MetricsReportingEnabled);
@@ -70,8 +74,14 @@ class ChromeMetricsServiceAccessor : public MetricsServiceAccessor {
   // registered at a time for a given trial name. Only the last group name that
   // is registered for a given trial name will be recorded. The values passed
   // in must not correspond to any real field trial in the code.
-  static bool RegisterSyntheticFieldTrial(const std::string& trial,
-                                          const std::string& group);
+  static bool RegisterSyntheticFieldTrial(const std::string& trial_name,
+                                          const std::string& group_name);
+
+  // Same as RegisterSyntheticFieldTrial above, but takes a hash for the trial
+  // name, rather than computing it from the string.
+  static bool RegisterSyntheticFieldTrialWithNameHash(
+      uint32_t trial_name_hash,
+      const std::string& group_name);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChromeMetricsServiceAccessor);
 };

chrome/browser/metrics/metrics_service_accessor.cc

@@ -7,7 +7,6 @@
 #include "chrome/browser/browser_process.h"
 #include "components/metrics/metrics_service.h"
 #include "components/metrics/metrics_service_observer.h"
-#include "components/variations/metrics_util.h"
 
 // static
 void MetricsServiceAccessor::AddMetricsServiceObserver(
@@ -27,13 +26,12 @@ void MetricsServiceAccessor::RemoveMetricsServiceObserver(
 // static
 bool MetricsServiceAccessor::RegisterSyntheticFieldTrial(
     MetricsService* metrics_service,
-    const std::string& trial,
-    const std::string& group) {
+    uint32_t trial_name_hash,
+    uint32_t group_name_hash) {
   if (!metrics_service)
     return false;
 
-  SyntheticTrialGroup trial_group(metrics::HashName(trial),
-                                  metrics::HashName(group));
+  SyntheticTrialGroup trial_group(trial_name_hash, group_name_hash);
   metrics_service->RegisterSyntheticFieldTrial(trial_group);
   return true;
 }

chrome/browser/metrics/metrics_service_accessor.h

@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_METRICS_METRICS_SERVICE_ACCESSOR_H_
 #define CHROME_BROWSER_METRICS_METRICS_SERVICE_ACCESSOR_H_
 
+#include <stdint.h>
 #include <string>
 
 #include "base/macros.h"
@@ -26,16 +27,13 @@ class MetricsServiceAccessor {
   static void AddMetricsServiceObserver(MetricsServiceObserver* observer);
   static void RemoveMetricsServiceObserver(MetricsServiceObserver* observer);
 
-  // Registers a field trial name and group to be used to annotate a UMA report
-  // with a particular Chrome configuration state. A UMA report will be
-  // annotated with this trial group if and only if all events in the report
-  // were created after the trial is registered. Only one group name may be
-  // registered at a time for a given trial name. Only the last group name that
-  // is registered for a given trial name will be recorded. The values passed
-  // in must not correspond to any real field trial in the code.
+  // Registers the specified synthetic field trial (identified by a hash of the
+  // trial name and group name) with |metrics_service|, if the service is not
+  // NULL, returning true on success.
+  // See the comment on MetricsService::RegisterSyntheticFieldTrial for details.
   static bool RegisterSyntheticFieldTrial(MetricsService* metrics_service,
-                                          const std::string& trial,
-                                          const std::string& group);
+                                          uint32_t trial_name_hash,
+                                          uint32_t group_name_hash);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MetricsServiceAccessor);