Add support for variations controlled overriding UI strings to the variations service.

components/variations/variations_seed_processor.cc

Index: components/variations/variations_seed_processor.cc
diff --git a/components/variations/variations_seed_processor.cc b/components/variations/variations_seed_processor.cc
index e468e4e2d808cddef99f84c3c6414a3a1205eeb0..87912e8630ee663a5592665e23a640cb0f3da82f 100644
--- a/components/variations/variations_seed_processor.cc
+++ b/components/variations/variations_seed_processor.cc
@@ -4,10 +4,12 @@
 
 #include "components/variations/variations_seed_processor.h"
 
+#include <map>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
+#include "base/strings/utf_string_conversions.h"
 #include "components/variations/processed_study.h"
 #include "components/variations/study_filtering.h"
 #include "components/variations/variations_associated_data.h"
@@ -58,6 +60,17 @@ void RegisterVariationIds(const Study_Experiment& experiment,
   }
 }
 
+// Executes |callback| on every override defined by |experiment|.
+void ApplyUIStringOverrides(
+    const Study_Experiment& experiment,
+    const VariationsSeedProcessor::UIStringOverrideCallback& callback) {
+  for (int i = 0; i < experiment.override_ui_string_size(); ++i) {
+    const Study_Experiment_OverrideUIString& override =
+        experiment.override_ui_string(i);
+    callback.Run(override.name_hash(), base::UTF8ToUTF16(override.value()));
+  }
+}
+
 }  // namespace
 
 VariationsSeedProcessor::VariationsSeedProcessor() {
@@ -73,17 +86,19 @@ void VariationsSeedProcessor::CreateTrialsFromSeed(
     const base::Version& version,
     Study_Channel channel,
     Study_FormFactor form_factor,
-    const std::string& hardware_class) {
+    const std::string& hardware_class,
+    const UIStringOverrideCallback& override_callback) {
   std::vector<ProcessedStudy> filtered_studies;
   FilterAndValidateStudies(seed, locale, reference_date, version, channel,
                            form_factor, hardware_class, &filtered_studies);
 
   for (size_t i = 0; i < filtered_studies.size(); ++i)
-    CreateTrialFromStudy(filtered_studies[i]);
+    CreateTrialFromStudy(filtered_studies[i], override_callback);
 }
 
 void VariationsSeedProcessor::CreateTrialFromStudy(
-    const ProcessedStudy& processed_study) {
+    const ProcessedStudy& processed_study,
+    const UIStringOverrideCallback& override_callback) {
   const Study& study = *processed_study.study();
 
   // Check if any experiments need to be forced due to a command line
@@ -98,8 +113,11 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
                                                  experiment.name()));
       RegisterExperimentParams(study, experiment);
       RegisterVariationIds(experiment, study.name());
-      if (study.activation_type() == Study_ActivationType_ACTIVATION_AUTO)
+      if (study.activation_type() == Study_ActivationType_ACTIVATION_AUTO) {
         trial->group();
+        // UI Strings can only be overridden from ACTIVATION_AUTO experiments.
+        ApplyUIStringOverrides(experiment, override_callback);
+      }
 
       DVLOG(1) << "Trial " << study.name() << " forced by flag: "
                << experiment.forcing_flag();
@@ -127,6 +145,7 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
           base::FieldTrialList::kNoExpirationYear, 1, 1, randomization_type,
           randomization_seed, NULL));
 
+  bool has_overrides = false;
   for (int i = 0; i < study.experiment_size(); ++i) {
     const Study_Experiment& experiment = study.experiment(i);
     RegisterExperimentParams(study, experiment);
@@ -140,13 +159,31 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
       trial->AppendGroup(experiment.name(), experiment.probability_weight());
 
     RegisterVariationIds(experiment, study.name());
+
+    has_overrides = has_overrides || experiment.override_ui_string_size() > 0;
   }
 
   trial->SetForced();
-  if (processed_study.is_expired())
+  if (processed_study.is_expired()) {
     trial->Disable();
-  else if (study.activation_type() == Study_ActivationType_ACTIVATION_AUTO)
-    trial->group();
+  } else if (study.activation_type() == Study_ActivationType_ACTIVATION_AUTO) {
+    const std::string& group_name = trial->group_name();
+
+    // Don't try to apply overrides if none of the experiments in this study had
+    // any.
+    if (!has_overrides)
+      return;
+
+    // UI Strings can only be overridden from ACTIVATION_AUTO experiments.
+    int experiment_index = processed_study.GetExperimentIndexByName(group_name);
+
+    // The field trial was defined from |study|, so the active experiment's name
+    // must be in the |study|.
+    DCHECK_NE(-1, experiment_index);
+
+    ApplyUIStringOverrides(study.experiment(experiment_index),
+                           override_callback);
+  }
 }
 
 }  // namespace chrome_variations