Python client side support for launch_app command of chromedriver:

/session/$sessionId/chromium/launch_app

This is using the approach first proposed by @richardrb
in pull request SeleniumHQ#168

py/selenium/webdriver/chrome/remote_connection.py

@@ -0,0 +1,25 @@
+# Licensed to the Software Freedom Conservancy (SFC) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The SFC licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from selenium.webdriver.remote.remote_connection import RemoteConnection
+
+class ChromeRemoteConnection(RemoteConnection):
+
+    def __init__(self, remote_server_addr, keep_alive=True):
+        RemoteConnection.__init__(self, remote_server_addr, keep_alive)
+        self._commands["launchApp"] = ('POST',
+            '/session/$sessionId/chromium/launch_app')

py/selenium/webdriver/chrome/webdriver.py

@@ -16,6 +16,7 @@
 # under the License.
 
 import base64
+from remote_connection import ChromeRemoteConnection
 from selenium.webdriver.remote.command import Command
 from selenium.webdriver.remote.webdriver import WebDriver as RemoteWebDriver
 from selenium.common.exceptions import WebDriverException
@@ -61,14 +62,18 @@ def __init__(self, executable_path="chromedriver", port=0,
 
         try:
             RemoteWebDriver.__init__(self,
-                command_executor=self.service.service_url,
-                desired_capabilities=desired_capabilities,
-                keep_alive=True)
+                command_executor=ChromeRemoteConnection(
+                    remote_server_addr=self.service.service_url),
+                desired_capabilities=desired_capabilities)
         except:
             self.quit()
             raise
         self._is_remote = False
 
+    def launch_app(self, id):
+        """Launches Chrome app specified by id."""
+        return self.execute("launchApp", {'id': id})
+
     def quit(self):
         """
         Closes the browser and shuts down the ChromeDriver executable