Declare private, constant list as ImmutableList.

The theory is that it's safer. The field is intended to be immutable, so accidental attempts to mutate it will be compile errors rather than runtime errors.

java/client/src/org/openqa/selenium/chrome/ChromeDriverCommandExecutor.java

@@ -18,20 +18,17 @@
 package org.openqa.selenium.chrome;
 
 import com.google.common.collect.ImmutableMap;
-
 import org.openqa.selenium.remote.CommandInfo;
 import org.openqa.selenium.remote.http.HttpMethod;
 import org.openqa.selenium.remote.service.DriverCommandExecutor;
 import org.openqa.selenium.remote.service.DriverService;
 
-import java.util.Map;
-
 /**
  * {@link DriverCommandExecutor} that understands ChromeDriver specific commands.
  */
 class ChromeDriverCommandExecutor extends DriverCommandExecutor {
 
-  private static final Map<String, CommandInfo> CHROME_COMMAND_NAME_TO_URL = ImmutableMap.of(
+  private static final ImmutableMap<String, CommandInfo> CHROME_COMMAND_NAME_TO_URL = ImmutableMap.of(
       ChromeDriverCommand.LAUNCH_APP,
       new CommandInfo("/session/:sessionId/chromium/launch_app", HttpMethod.POST));