Reuse SmartGson.getReader() in JenkinsCiPluginsRepository

JenkinsCiPluginsRepository was reading directly from a URI when fetching
a remote stream rather than relying on the SmartGson.getReader(), which
had exactly the same logic.

Use a unique channel to fetch from a remote source so that mocking
becomes easier and also replacing it with a different transport handler
would not require changes to the JenkinsCiPluginsRepository
implementation.

Change-Id: Ib1f25e7085cafb1c133e1b7e48dc993328489254

src/main/java/com/googlesource/gerrit/plugins/manager/gson/SmartGson.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/manager/gson/SmartGson.java b/src/main/java/com/googlesource/gerrit/plugins/manager/gson/SmartGson.java
index 21b1ddf..fa2860f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/manager/gson/SmartGson.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/manager/gson/SmartGson.java
@@ -48,7 +48,7 @@
     }
   }
 
-  private InputStreamReader getReader(String url) throws IOException {
+  public InputStreamReader getReader(String url) throws IOException {
     URL ciUrl;
     try {
       ciUrl = URI.create(url).toURL();

src/main/java/com/googlesource/gerrit/plugins/manager/repository/JenkinsCiPluginsRepository.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/manager/repository/JenkinsCiPluginsRepository.java b/src/main/java/com/googlesource/gerrit/plugins/manager/repository/JenkinsCiPluginsRepository.java
index 48dac31..4541e01 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/manager/repository/JenkinsCiPluginsRepository.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/manager/repository/JenkinsCiPluginsRepository.java
@@ -14,8 +14,6 @@
 
 package com.googlesource.gerrit.plugins.manager.repository;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.flogger.FluentLogger;
 import com.google.gson.JsonArray;
@@ -31,8 +29,6 @@
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.InputStreamReader;
-import java.net.URI;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -225,8 +221,7 @@
               "%s/artifact/%s",
               buildExecution.getString("url"), verArtifactJson.get().getString("relativePath"));
       try (BufferedReader reader =
-          new BufferedReader(
-              new InputStreamReader(URI.create(versionUrl).toURL().openStream(), UTF_8), 4096)) {
+          new BufferedReader(gsonProvider.get().getReader(versionUrl), 4096)) {
         String line;
         while ((line = reader.readLine()) != null) {
           if (artifactBody.length() > 0) {