Add and implement API to associate Google experiment IDs with FieldTrials.

This includes unit tests for the API, but no uses yet.

This change also involves exposing a new MakeGroupNameId static helper in FieldTrial to assist with the usage of this new API.

BUG=121988
TEST=Ensure that unit_tests  GoogleExperimentsTest.* pass.

Review URL: http://codereview.chromium.org/9965086

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@133212 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 14 insertions, 0 deletions

diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index e04c86e..e53fdf3 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -168,6 +168,16 @@ std::string FieldTrial::MakeName(const std::string& name_prefix,
 }
 
 // static
+FieldTrial::NameGroupId FieldTrial::MakeNameGroupId(
+    const std::string& trial_name,
+    const std::string& group_name) {
+  NameGroupId id;
+  id.name = HashName(trial_name);
+  id.group = HashName(group_name);
+  return id;
+}
+
+// static
 void FieldTrial::EnableBenchmarking() {
   DCHECK_EQ(0u, FieldTrialList::GetFieldTrialCount());
   enable_benchmarking_ = true;
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index 2852393..be58a93 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -146,6 +146,10 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   static std::string MakeName(const std::string& name_prefix,
                               const std::string& trial_name);
 
+  // Helper function to create a NameGroupId from |trial_name| and |group_name|.
+  static NameGroupId MakeNameGroupId(const std::string& trial_name,
+                                     const std::string& group_name);
+
   // Enable benchmarking sets field trials to a common setting.
   static void EnableBenchmarking();