Try setting an implicit wait of maybe 10 seconds.
gmail.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
Or set an explicit wait. An explicit wait is a code you define to wait for a certain condition to occur before proceeding further in the code. In your case, it is the visibility of the password input field.
WebDriverWait wait = new WebDriverWait(gmail, 10);
WebElement element = wait.until(
ExpectedConditions.visibilityOfElementLocated(By.id("Passwd")));
gmail.findElement(By.id("Passwd")).sendKeys("xyz");