[Field trial params] Getting field trial params by feature name in Java.

chrome/browser/android/chrome_feature_list.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/chrome_feature_list.h"
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/android/jni_string.h"
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial_params.h"
 #include "chrome/common/chrome_features.h"
 #include "components/autofill/core/browser/autofill_experiments.h"
 #include "components/ntp_snippets/features.h"
 #include "components/offline_pages/core/offline_page_feature.h"
 #include "components/password_manager/core/common/password_manager_features.h"
 #include "content/public/common/content_features.h"
 #include "jni/ChromeFeatureList_jni.h"
 
 using base::android::ConvertJavaStringToUTF8;
+using base::android::ConvertUTF8ToJavaString;
 using base::android::JavaParamRef;
+using base::android::ScopedJavaLocalRef;
 
 namespace chrome {
 namespace android {
 
 namespace {
 
 // Array of features exposed through the Java ChromeFeatureList API. Entries in
 // this array may either refer to features defined in the header of this file or
 // in other locations in the code base (e.g. chrome/, components/, etc).
 const base::Feature* kFeaturesExposedToJava[] = {
@@ skipping 115 matching lines @@
   const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
   for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
     if (kFeaturesExposedToJava[i]->name == feature_name)
       return base::FeatureList::IsEnabled(*kFeaturesExposedToJava[i]);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();
   return false;
 }
 
+static ScopedJavaLocalRef<jstring> GetFieldTrialParamByFeature(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name) {
+  const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
+  const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {

[Alexei Svitkine (slow), 2017/02/08 16:36:00]

Nit: Since we loop over features in all of these functions, how about a helper
function to find the feature?

[jkrcal, 2017/02/09 10:00:45]

Good point, done!

+    if (kFeaturesExposedToJava[i]->name == feature_name) {
+      std::string param_value = base::GetFieldTrialParamValueByFeature(
+          *kFeaturesExposedToJava[i], param_name);
+      return ConvertUTF8ToJavaString(env, param_value);
+    }
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
+  return ConvertUTF8ToJavaString(env, std::string());
+}
+
 static jint GetFieldTrialParamByFeatureAsInt(
     JNIEnv* env,
     const JavaParamRef<jclass>& clazz,
     const JavaParamRef<jstring>& jfeature_name,
     const JavaParamRef<jstring>& jparam_name,
     const jint jdefault_value) {
   const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
   const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
   int default_value = static_cast<int>(jdefault_value);
 
   for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
     if (kFeaturesExposedToJava[i]->name == feature_name)
       return base::GetFieldTrialParamByFeatureAsInt(
           *kFeaturesExposedToJava[i], param_name, default_value);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();
   return jdefault_value;
 }
 
+static jdouble GetFieldTrialParamByFeatureAsDouble(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name,
+    const jdouble jdefault_value) {
+  const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
+  const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+  double default_value = static_cast<double>(jdefault_value);
+
+  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
+    if (kFeaturesExposedToJava[i]->name == feature_name)
+      return base::GetFieldTrialParamByFeatureAsDouble(
+          *kFeaturesExposedToJava[i], param_name, default_value);
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
+  return jdefault_value;
+}
+
+static jboolean GetFieldTrialParamByFeatureAsBoolean(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name,
+    const jboolean jdefault_value) {
+  const std::string feature_name = ConvertJavaStringToUTF8(env, jfeature_name);
+  const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+  bool default_value = static_cast<bool>(jdefault_value);
+
+  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
+    if (kFeaturesExposedToJava[i]->name == feature_name)
+      return base::GetFieldTrialParamByFeatureAsBool(
+          *kFeaturesExposedToJava[i], param_name, default_value);
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
+  return jdefault_value;
+}
+
 bool RegisterChromeFeatureListJni(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace chrome