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

chrome/browser/android/chrome_feature_list.cc

Index: chrome/browser/android/chrome_feature_list.cc
diff --git a/chrome/browser/android/chrome_feature_list.cc b/chrome/browser/android/chrome_feature_list.cc
index 5c03d74f36903523914fa2cef46f9923c30b3efc..8ef5c5e2d131dfd87e26717311ea4a89bd5e92ad 100644
--- a/chrome/browser/android/chrome_feature_list.cc
+++ b/chrome/browser/android/chrome_feature_list.cc
@@ -21,7 +21,9 @@
 #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 {
@@ -72,6 +74,14 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &password_manager::features::kViewPasswords,
 };
 
+const base::Feature* FindFeatureExposedToJava(const std::string& feature_name) {
+  for (size_t i = 0; i < arraysize(kFeaturesExposedToJava); ++i) {
+    if (kFeaturesExposedToJava[i]->name == feature_name)
+      return kFeaturesExposedToJava[i];
+  }
+  return nullptr;
+}
+
 }  // namespace
 
 // Alphabetical:
@@ -151,30 +161,81 @@ const base::Feature kWebVRCardboardSupport{
 static jboolean IsEnabled(JNIEnv* env,
                           const JavaParamRef<jclass>& clazz,
                           const JavaParamRef<jstring>& jfeature_name) {
-  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]);
-  }
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr)
+    return base::FeatureList::IsEnabled(*feature);
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();

[Bernhard Bauer, 2017/02/09 17:04:29]

The NOTREACHED() made sense in the old version where the compiler requires a
return value, but here you have a check, and then code that handles when the
check fails, which is not allowed per the style guide. Just DCHECK(feature) and
return base::FeatureList::IsEnabled(*feature).

[jkrcal, 2017/02/09 19:10:40]

Ah, sure! Thanks!

I've moved the DCHECK into the helper function to make it even crisper.

   return false;
 }
 
+static ScopedJavaLocalRef<jstring> GetFieldTrialParamByFeature(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name) {
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    std::string param_value =
+        base::GetFieldTrialParamValueByFeature(*feature, 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);
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsInt(*feature, param_name,
+                                                  jdefault_value);
+  }
+  // Features queried via this API must be present in |kFeaturesExposedToJava|.
+  NOTREACHED();
+  return 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);
+static jdouble GetFieldTrialParamByFeatureAsDouble(
+    JNIEnv* env,
+    const JavaParamRef<jclass>& clazz,
+    const JavaParamRef<jstring>& jfeature_name,
+    const JavaParamRef<jstring>& jparam_name,
+    const jdouble jdefault_value) {
+  const base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsDouble(*feature, param_name,
+                                                     jdefault_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 base::Feature* feature =
+      FindFeatureExposedToJava(ConvertJavaStringToUTF8(env, jfeature_name));
+  if (feature != nullptr) {
+    const std::string param_name = ConvertJavaStringToUTF8(env, jparam_name);
+    return base::GetFieldTrialParamByFeatureAsBool(*feature, param_name,
+                                                   jdefault_value);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();