[java] deprecate setHeadless method on FirefoxOptions

Author: titusfortner

java/src/org/openqa/selenium/firefox/FirefoxOptions.java

@@ -252,6 +252,11 @@ public FirefoxOptions setLogLevel(FirefoxDriverLogLevel logLevel) {
     return setFirefoxOption(Keys.LOG, logLevel.toJson());
   }
 
+  /**
+   * @deprecated Use {@link #addArguments(String...)}.
+   * Example: `addArguments("-headless")`.
+   */
+  @Deprecated
   public FirefoxOptions setHeadless(boolean headless) {
     Object rawArgs = firefoxOptions.getOrDefault(Keys.ARGS.key(), new ArrayList<>());
     Require.stateCondition(rawArgs instanceof List, "Arg list of unexpected type: %s", rawArgs);

java/test/org/openqa/selenium/firefox/FirefoxDriverTest.java

@@ -362,7 +362,7 @@ public void canSetPageLoadStrategyViaOptions() {
   @Test
   @NoDriverBeforeTest
   public void canStartHeadless() {
-    localDriver = new FirefoxDriver(new FirefoxOptions().setHeadless(true));
+    localDriver = new FirefoxDriver(new FirefoxOptions().addArguments("-headless"));
 
     assertThat(((FirefoxDriver) localDriver).getCapabilities().getCapability("moz:headless")).isEqualTo(true);
   }

java/test/org/openqa/selenium/firefox/FirefoxOptionsTest.java

@@ -506,7 +506,7 @@ void mergingOptionsWithOptionsAsMutableCapabilities() throws IOException {
   void firefoxOptionsShouldEqualEquivalentImmutableCapabilities() {
     FirefoxOptions
       options =
-      new FirefoxOptions().addArguments("hello").setPageLoadStrategy(EAGER).setHeadless(true);
+      new FirefoxOptions().addArguments("hello", "-headless").setPageLoadStrategy(EAGER);
     Capabilities caps = new ImmutableCapabilities(options);
 
     assertThat(caps).isEqualTo(options);

java/test/org/openqa/selenium/testing/drivers/Browser.java

@@ -125,7 +125,7 @@ public Capabilities getCapabilities() {
       }
 
       if (Boolean.getBoolean("webdriver.headless")) {
-        options.setHeadless(true);
+        options.addArguments("-headless");
       }
 
       return options;