[Chromedriver] Add Device Metrics override support to ChromeDriver via Capabilities

chrome/test/chromedriver/test/webserver.py

Index: chrome/test/chromedriver/test/webserver.py
diff --git a/chrome/test/chromedriver/test/webserver.py b/chrome/test/chromedriver/test/webserver.py
index 716e0f4a9b47d96cf4775667e6e9ff4df580952f..9de03395b9f744cee3fbaf7f4f743f00fb1735fc 100644
--- a/chrome/test/chromedriver/test/webserver.py
+++ b/chrome/test/chromedriver/test/webserver.py
@@ -48,6 +48,9 @@ class Request(object):
   def GetPath(self):
     return self._handler.path
 
+  def GetHeader(self, name):
+    return self._handler.headers.getheader(name)
+
 
 class _BaseServer(BaseHTTPServer.HTTPServer):
   """Internal server that throws if timed out waiting for a request."""
@@ -120,19 +123,28 @@ class WebServer(object):
     self._thread.daemon = True
     self._thread.start()
     self._path_data_map = {}
-    self._path_data_lock = threading.Lock()
+    self._path_callback_map = {}
+    self._path_maps_lock = threading.Lock()
 
   def _OnRequest(self, request, responder):
     path = request.GetPath().split('?')[0]
 
-    # Serve from path -> data map.
-    self._path_data_lock.acquire()
+    # Serve from path -> callback and data maps.
+    self._path_maps_lock.acquire()
     try:
+      if path in self._path_callback_map:
+        body = self._path_callback_map[path](request)
+        if body:
+          responder.SendResponse(body)
+        else:
+          responder.SendError(503)
+        return
+
       if path in self._path_data_map:
         responder.SendResponse(self._path_data_map[path])
         return
     finally:
-      self._path_data_lock.release()
+      self._path_maps_lock.release()
 
     # Serve from file.
     path = os.path.normpath(
@@ -146,11 +158,19 @@ class WebServer(object):
     responder.SendResponseFromFile(path)
 
   def SetDataForPath(self, path, data):
-    self._path_data_lock.acquire()
+    self._path_maps_lock.acquire()
     try:
       self._path_data_map[path] = data
     finally:
-      self._path_data_lock.release()
+      self._path_maps_lock.release()
+
+  def SetCallbackForPath(self, path, func):
+    self._path_maps_lock.acquire()
+    try:
+      self._path_callback_map[path] = func
+    finally:
+      self._path_maps_lock.release()
+
 
   def GetUrl(self):
     """Returns the base URL of the server."""