Import //fetch from Web Platform Tests.

third_party/WebKit/LayoutTests/external/wpt/fetch/api/resources/preflight.py

+def main(request, response):
+    headers = [("Content-Type", "text/plain")]
+    stashed_data = {'control_request_headers': "", 'preflight': "0", 'preflight_referrer': ""}
+
+    token = None
+    if "token" in request.GET:
+        token = request.GET.first("token")
+
+    if "origin" in request.GET:
+        for origin in request.GET['origin'].split(", "):
+            headers.append(("Access-Control-Allow-Origin", origin))
+    else:
+        headers.append(("Access-Control-Allow-Origin", "*"))
+
+    if "credentials" in request.GET:
+        headers.append(("Access-Control-Allow-Credentials", "true"))
+
+    if request.method == "OPTIONS":
+        if not "Access-Control-Request-Method" in request.headers:
+            response.set_error(400, "No Access-Control-Request-Method header")
+            return "ERROR: No access-control-request-method in preflight!"
+
+        if "control_request_headers" in request.GET:
+            stashed_data['control_request_headers'] = request.headers.get("Access-Control-Request-Headers", None)
+
+        if "max_age" in request.GET:
+            headers.append(("Access-Control-Max-Age", request.GET['max_age']))
+
+        if "allow_headers" in request.GET:
+            headers.append(("Access-Control-Allow-Headers", request.GET['allow_headers']))
+
+        if "allow_methods" in request.GET:
+            headers.append(("Access-Control-Allow-Methods", request.GET['allow_methods']))
+
+        preflight_status = 200
+        if "preflight_status" in request.GET:
+            preflight_status = int(request.GET.first("preflight_status"))
+
+        stashed_data['preflight'] = "1"
+        stashed_data['preflight_referrer'] = request.headers.get("Referer", "")
+        if token:
+            request.server.stash.put(token, stashed_data)
+
+        return preflight_status, headers, ""
+
+
+    if token:
+        data = request.server.stash.take(token)
+        if data:
+            stashed_data = data
+
+    #use x-* headers for returning value to bodyless responses
+    headers.append(("Access-Control-Expose-Headers", "x-did-preflight, x-control-request-headers, x-referrer, x-preflight-referrer, x-origin"))
+    headers.append(("x-did-preflight", stashed_data['preflight']))
+    if stashed_data['control_request_headers'] != None:
+      headers.append(("x-control-request-headers", stashed_data['control_request_headers']))
+    headers.append(("x-preflight-referrer", stashed_data['preflight_referrer']))
+    headers.append(("x-referrer", request.headers.get("Referer", "") ))
+    headers.append(("x-origin", request.headers.get("Origin", "") ))
+
+    if token:
+      request.server.stash.put(token, stashed_data)
+
+    return headers, ""