Revert 84197 - Add one-time randomization support for FieldTrial, and the ability to

base/metrics/field_trial.cc

Index: base/metrics/field_trial.cc
===================================================================
--- base/metrics/field_trial.cc	(revision 84367)
+++ base/metrics/field_trial.cc	(working copy)
@@ -6,8 +6,6 @@
 
 #include "base/logging.h"
 #include "base/rand_util.h"
-#include "base/sha1.h"
-#include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
 
@@ -43,13 +41,11 @@
   : name_(name),
     divisor_(total_probability),
     default_group_name_(default_group_name),
-    random_(static_cast<Probability>(divisor_ * RandDouble())),
+    random_(static_cast<Probability>(divisor_ * base::RandDouble())),
     accumulated_group_probability_(0),
-    next_group_number_(kDefaultGroupNumber + 1),
-    group_(kNotFinalized),
-    enable_field_trial_(true) {
+    next_group_number_(kDefaultGroupNumber+1),
+    group_(kNotFinalized) {
   DCHECK_GT(total_probability, 0);
-  DCHECK(!name_.empty());
   DCHECK(!default_group_name_.empty());
   FieldTrialList::Register(this);
 
@@ -59,7 +55,7 @@
   DCHECK_GT(day_of_month, 0);
   DCHECK_LT(day_of_month, 32);
 
-  Time::Exploded exploded;
+  base::Time::Exploded exploded;
   exploded.year = year;
   exploded.month = month;
   exploded.day_of_week = 0;  // Should be unused.
@@ -69,41 +65,16 @@
   exploded.second = 0;
   exploded.millisecond = 0;
 
-  Time expiration_time = Time::FromLocalExploded(exploded);
-  if (GetBuildTime() > expiration_time)
-    Disable();
+  base::Time expiration_time = Time::FromLocalExploded(exploded);
+  disable_field_trial_ = (GetBuildTime() > expiration_time) ? true : false;
 }
 
-void FieldTrial::UseOneTimeRandomization() {
-  DCHECK_EQ(group_, kNotFinalized);
-  DCHECK_EQ(kDefaultGroupNumber + 1, next_group_number_);
-  if (!FieldTrialList::IsOneTimeRandomizationEnabled()) {
-    NOTREACHED();
-    Disable();
-    return;
-  }
-
-  random_ = static_cast<Probability>(
-      divisor_ * HashClientId(FieldTrialList::client_id(), name_));
-}
-
-void FieldTrial::Disable() {
-  enable_field_trial_ = false;
-
-  // In case we are disabled after initialization, we need to switch
-  // the trial to the default group.
-  if (group_ != kNotFinalized) {
-    group_ = kDefaultGroupNumber;
-    group_name_ = default_group_name_;
-  }
-}
-
 int FieldTrial::AppendGroup(const std::string& name,
                             Probability group_probability) {
   DCHECK_LE(group_probability, divisor_);
   DCHECK_GE(group_probability, 0);
 
-  if (enable_benchmarking_ || !enable_field_trial_)
+  if (enable_benchmarking_ || disable_field_trial_)
     group_probability = 0;
 
   accumulated_group_probability_ += group_probability;
@@ -113,7 +84,7 @@
     // This is the group that crossed the random line, so we do the assignment.
     group_ = next_group_number_;
     if (name.empty())
-      StringAppendF(&group_name_, "%d", group_);
+      base::StringAppendF(&group_name_, "%d", group_);
     else
       group_name_ = name;
     FieldTrialList::NotifyFieldTrialGroupSelection(name_, group_name_);
@@ -132,8 +103,7 @@
 }
 
 std::string FieldTrial::group_name() {
-  group();  // call group() to make sure group assignment was done.
-  DCHECK(!group_name_.empty());
+  group();  // call group() to make group assignment was done.
   return group_name_;
 }
 
@@ -163,25 +133,6 @@
   return integral_build_time;
 }
 
-// static
-double FieldTrial::HashClientId(const std::string& client_id,
-                                const std::string& trial_name) {
-  // SHA-1 is designed to produce a uniformly random spread in its output space,
-  // even for nearly-identical inputs, so it helps massage whatever client_id
-  // and trial_name we get into something with a uniform distribution, which
-  // is desirable so that we don't skew any part of the 0-100% spectrum.
-  std::string input(client_id + trial_name);
-  unsigned char sha1_hash[SHA1_LENGTH];
-  SHA1HashBytes(reinterpret_cast<const unsigned char*>(input.c_str()),
-                input.size(),
-                sha1_hash);
-
-  COMPILE_ASSERT(sizeof(uint64) < sizeof(sha1_hash), need_more_data);
-  uint64* bits = reinterpret_cast<uint64*>(&sha1_hash[0]);
-
-  return BitsToOpenEndedUnitInterval(*bits);
-}
-
 //------------------------------------------------------------------------------
 // FieldTrialList methods and members.
 
@@ -191,9 +142,8 @@
 // static
 bool FieldTrialList::register_without_global_ = false;
 
-FieldTrialList::FieldTrialList(const std::string& client_id)
+FieldTrialList::FieldTrialList()
     : application_start_time_(TimeTicks::Now()),
-      client_id_(client_id),
       observer_list_(ObserverList<Observer>::NOTIFY_EXISTING_ONLY) {
   DCHECK(!global_);
   DCHECK(!register_without_global_);
@@ -254,23 +204,19 @@
 }
 
 // static
-bool FieldTrialList::TrialExists(const std::string& name) {
-  return Find(name) != NULL;
-}
-
-// static
 void FieldTrialList::StatesToString(std::string* output) {
   if (!global_)
     return;
   DCHECK(output->empty());
   AutoLock auto_lock(global_->lock_);
-
   for (RegistrationList::iterator it = global_->registered_.begin();
        it != global_->registered_.end(); ++it) {
     const std::string name = it->first;
     std::string group_name = it->second->group_name_internal();
     if (group_name.empty())
-      continue;  // Should not include uninitialized trials.
+      // No definitive winner in this trial, use default_group_name as the
+      // group_name.
+      group_name = it->second->default_group_name();
     DCHECK_EQ(name.find(kPersistentStringSeparator), std::string::npos);
     DCHECK_EQ(group_name.find(kPersistentStringSeparator), std::string::npos);
     output->append(name);
@@ -367,24 +313,6 @@
   return global_->registered_.size();
 }
 
-// static
-bool FieldTrialList::IsOneTimeRandomizationEnabled() {
-  DCHECK(global_);
-  if (!global_)
-    return false;
-
-  return !global_->client_id_.empty();
-}
-
-// static
-const std::string& FieldTrialList::client_id() {
-  DCHECK(global_);
-  if (!global_)
-    return EmptyString();
-
-  return global_->client_id_;
-}
-
 FieldTrial* FieldTrialList::PreLockedFind(const std::string& name) {
   RegistrationList::iterator it = registered_.find(name);
   if (registered_.end() == it)