downgrade logback and remove unused.

Author: zhumin8

oauth2_http/java/com/google/auth/oauth2/ServiceAccountCredentials.java

@@ -64,7 +64,6 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
-import com.google.gson.Gson;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.ObjectInputStream;
@@ -99,7 +98,6 @@ public class ServiceAccountCredentials extends GoogleCredentials
   private static final int TWELVE_HOURS_IN_SECONDS = 43200;
   private static final int DEFAULT_LIFETIME_IN_SECONDS = 3600;
   private static final Logger LOGGER = LoggingUtils.getLogger(ServiceAccountCredentials.class);
-  private static final Gson gson = new Gson();
 
   private final String clientId;
   private final String clientEmail;

oauth2_http/java/com/google/auth/oauth2/UserCredentials.java

@@ -50,7 +50,6 @@
 import com.google.auth.oauth2.MetricsUtils.RequestType;
 import com.google.common.base.MoreObjects;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
-import com.google.gson.Gson;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -71,7 +70,6 @@ public class UserCredentials extends GoogleCredentials implements IdTokenProvide
   private static final String PARSE_ERROR_PREFIX = "Error parsing token refresh response. ";
   private static final long serialVersionUID = -4800758775038679176L;
   private static final Logger LOGGER = LoggingUtils.getLogger(UserCredentials.class);
-  private static final Gson gson = new Gson();
 
   private final String clientId;
   private final String clientSecret;

oauth2_http/pom.xml

@@ -257,26 +257,14 @@
     <dependency>
       <groupId>ch.qos.logback</groupId>
       <artifactId>logback-classic</artifactId>
-      <version>1.5.11</version>
+      <!--   Latest version with java8 support   -->
+      <version>1.3.14</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>ch.qos.logback</groupId>
       <artifactId>logback-core</artifactId>
-      <version>1.5.11</version>
-      <scope>test</scope>
-    </dependency>
-    <!--  For formatting and filtering, may remove after setting up tests  -->
-    <dependency>
-      <groupId>net.logstash.logback</groupId>
-      <artifactId>logstash-logback-encoder</artifactId>
-      <version>8.0</version>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.codehaus.janino</groupId>
-      <artifactId>janino</artifactId>
-      <version>3.1.9</version>
+      <version>1.3.14</version>
       <scope>test</scope>
     </dependency>