Updating IE driver for allowed commands when alert is present

The W3C WebDriver Specification allows getting the current window handles,
the list of currently available window handles, and switching to a window
(in certain cases) while an alert is present. This commit now allows the
IE driver to do so without throwing an UnexpectedAlertException.

Author: jimevans

cpp/iedriver/IECommandExecutor.cpp

@@ -474,7 +474,10 @@ void IECommandExecutor::DispatchCommand() {
               command_type == webdriver::CommandType::SendKeysToAlert ||
               command_type == webdriver::CommandType::AcceptAlert ||
               command_type == webdriver::CommandType::DismissAlert ||
-              command_type == webdriver::CommandType::SetAlertCredentials) {
+              command_type == webdriver::CommandType::SetAlertCredentials ||
+              command_type == webdriver::CommandType::GetCurrentWindowHandle ||
+              command_type == webdriver::CommandType::GetWindowHandles ||
+              command_type == webdriver::CommandType::SwitchToWindow) {
             LOG(DEBUG) << "Alert is detected, and the sent command is valid";
           } else {
             LOG(DEBUG) << "Unexpected alert is detected, and the sent command is invalid when an alert is present";