add a flag to enable/disable download interception on android

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>
 
@@ skipping 20 matching lines @@
 }  // namespace
 
 const base::Feature kNTPOfflinePagesFeature {
   "NTPOfflinePages", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
 const base::Feature kPhysicalWebFeature {
   "PhysicalWeb", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
+const base::Feature kSystemDownloadManager {
+  "SystemDownloadManager", base::FEATURE_ENABLED_BY_DEFAULT
+};
+
 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]);
   }
   // Features queried via this API must be present in |kFeaturesExposedToJava|.
   NOTREACHED();
   return false;
 }
 
 bool RegisterChromeFeatureListJni(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace android
 }  // namespace chrome