Revert "fix: Issue #1347: ExternalAccountCredentials serialization is broken" (#1359)

Author: BigTailWolf

google-auth-library-java/oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java

@@ -42,7 +42,6 @@
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.ObjectInputStream;
 import java.math.BigDecimal;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
@@ -541,13 +540,6 @@ public CredentialSource getCredentialSource() {
     return credentialSource;
   }
 
-  @SuppressWarnings("unused")
-  private void readObject(ObjectInputStream input) throws IOException, ClassNotFoundException {
-    // Properly deserialize the transient transportFactory.
-    input.defaultReadObject();
-    transportFactory = newInstance(transportFactoryClassName);
-  }
-
   @Nullable
   public String getServiceAccountImpersonationUrl() {
     return serviceAccountImpersonationUrl;

google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ExternalAccountCredentialsTest.java

@@ -1117,9 +1117,6 @@ public void serialize() throws IOException, ClassNotFoundException {
         testCredentials.getServiceAccountImpersonationOptions().getLifetime(),
         deserializedCredentials.getServiceAccountImpersonationOptions().getLifetime());
     assertSame(deserializedCredentials.clock, Clock.SYSTEM);
-    assertEquals(
-        MockExternalAccountCredentialsTransportFactory.class,
-        deserializedCredentials.toBuilder().getHttpTransportFactory().getClass());
   }
 
   @Test
@@ -1310,30 +1307,17 @@ protected TestCredentialSource(Map<String, Object> credentialSourceMap) {
       }
     }
 
-    @Override
-    public Builder toBuilder() {
-      return new Builder(this);
-    }
-
     public static Builder newBuilder() {
       return new Builder();
     }
 
     static class Builder extends ExternalAccountCredentials.Builder {
       Builder() {}
 
-      Builder(TestExternalAccountCredentials credentials) {
-        super(credentials);
-      }
-
       @Override
       public TestExternalAccountCredentials build() {
         return new TestExternalAccountCredentials(this);
       }
-
-      public HttpTransportFactory getHttpTransportFactory() {
-        return transportFactory;
-      }
     }
 
     protected TestExternalAccountCredentials(ExternalAccountCredentials.Builder builder) {