Componentize guts of ChromeMetricsServiceAccessor field trial functions

This CL turns ChromeMetricsServiceAccessor's field trials-related functions
into just thin wrappers around MetricsServiceAccessor functions in preparation
for decoupling the iOS port from ChromeMetricsServiceAccessor.

BUG=508014

Review URL: https://codereview.chromium.org/1374663003

Cr-Commit-Position: refs/heads/master@{#351308}

chrome/browser/metrics/chrome_metrics_service_accessor.cc

@@ -11,7 +11,6 @@
 #include "chrome/common/chrome_switches.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"
@@ -52,16 +51,15 @@ bool ChromeMetricsServiceAccessor::IsMetricsAndCrashReportingEnabled() {
 bool ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
     const std::string& trial_name,
     const std::string& group_name) {
-  return RegisterSyntheticFieldTrialWithNameHash(metrics::HashName(trial_name),
-                                                 group_name);
+  return metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrial(
+      g_browser_process->metrics_service(), trial_name, group_name);
 }
 
 // static
 bool ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameHash(
     uint32_t trial_name_hash,
     const std::string& group_name) {
-  return metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrial(
-      g_browser_process->metrics_service(),
-      trial_name_hash,
-      metrics::HashName(group_name));
+  return metrics::MetricsServiceAccessor::
+      RegisterSyntheticFieldTrialWithNameHash(
+          g_browser_process->metrics_service(), trial_name_hash, group_name);
 }

chrome/browser/metrics/chrome_metrics_service_accessor.h

@@ -94,18 +94,16 @@ class ChromeMetricsServiceAccessor : public metrics::MetricsServiceAccessor {
   // http://crbug.com/362192,  http://crbug.com/532084
   static bool IsMetricsAndCrashReportingEnabled();
 
-  // 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.
+  // Calls metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrial() with
+  // g_browser_process->metrics_service(). See that function's declaration for
+  // details.
   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.
+  // Calls
+  // metrics::MetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameHash()
+  // with g_browser_process->metrics_service(). See that function's declaration
+  // for details.
   static bool RegisterSyntheticFieldTrialWithNameHash(
       uint32_t trial_name_hash,
       const std::string& group_name);

components/metrics/metrics_service_accessor.cc

@@ -5,11 +5,30 @@
 #include "components/metrics/metrics_service_accessor.h"
 
 #include "components/metrics/metrics_service.h"
+#include "components/variations/metrics_util.h"
 
 namespace metrics {
 
 // static
 bool MetricsServiceAccessor::RegisterSyntheticFieldTrial(
+    MetricsService* metrics_service,
+    const std::string& trial_name,
+    const std::string& group_name) {
+  return RegisterSyntheticFieldTrialWithNameAndGroupHash(
+      metrics_service, HashName(trial_name), HashName(group_name));
+}
+
+// static
+bool MetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameHash(
+    MetricsService* metrics_service,
+    uint32_t trial_name_hash,
+    const std::string& group_name) {
+  return RegisterSyntheticFieldTrialWithNameAndGroupHash(
+      metrics_service, trial_name_hash, HashName(group_name));
+}
+
+// static
+bool MetricsServiceAccessor::RegisterSyntheticFieldTrialWithNameAndGroupHash(
     MetricsService* metrics_service,
     uint32_t trial_name_hash,
     uint32_t group_name_hash) {

components/metrics/metrics_service_accessor.h

@@ -6,6 +6,7 @@
 #define COMPONENTS_METRICS_METRICS_SERVICE_ACCESSOR_H_
 
 #include <stdint.h>
+#include <string>
 
 #include "base/macros.h"
 
@@ -22,11 +23,29 @@ class MetricsServiceAccessor {
   // disallow instantiation.
   MetricsServiceAccessor() {}
 
-  // 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.
+  // Registers a field trial name and group with |metrics_service| (if not
+  // null), to be used to annotate a UMA report with a particular 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. Returns true on success.
   // See the comment on MetricsService::RegisterSyntheticFieldTrial for details.
-  static bool RegisterSyntheticFieldTrial(
+  static bool RegisterSyntheticFieldTrial(MetricsService* metrics_service,
+                                          const std::string& trial_name,
+                                          const std::string& group_name);
+
+  // Same as RegisterSyntheticFieldTrial above, but takes in the trial name as a
+  // hash rather than computing the hash from the string.
+  static bool RegisterSyntheticFieldTrialWithNameHash(
+      MetricsService* metrics_service,
+      uint32_t trial_name_hash,
+      const std::string& group_name);
+
+  // Same as RegisterSyntheticFieldTrial above, but takes in the trial and group
+  // names as hashes rather than computing those hashes from the strings.
+  static bool RegisterSyntheticFieldTrialWithNameAndGroupHash(
       MetricsService* metrics_service,
       uint32_t trial_name_hash,
       uint32_t group_name_hash);