isolateserver: add checkbox to enable ts_mon

appengine/isolate/config.py

Index: appengine/isolate/config.py
diff --git a/appengine/isolate/config.py b/appengine/isolate/config.py
index 3404952318f6aa87af164f1cedf868a97ad88fb0..b9fa8b62c6dd302f87c5bf307eb3e1e38a111fba 100644
--- a/appengine/isolate/config.py
+++ b/appengine/isolate/config.py
@@ -55,6 +55,26 @@ class GlobalConfig(config.GlobalConfig):
     self.global_secret = os.urandom(16)
     self.gs_bucket = app_identity.get_application_id()
 
+  @classmethod

[M-A Ruel, 2016/02/19 02:44:40]

This code belongs to the frontend in my opinion, not here.

[Sergey Berezin, 2016/02/19 20:35:32]

IMHO, keeping the type conversion closer to the definition of the parameters is
more intuitive. You only need to modify one class (and one file) when updating
the types, and the cast can be reused in other places, not just in the handler.

But the way it's set up now, the handler still needs to know all the parameters
anyway, so I don't feel strongly about it. Your call.

[M-A Ruel, 2016/02/19 20:37:26]

Yes but this function is purely related to form like behavior. If it were an API
for example, the format would be different. Because it is about a web form, this
is leaking the abstraction layer too low, that's why it should be in
handlers_frontend.

[Sergey Berezin, 2016/02/19 20:46:51]

OK, done.

+  def cast_to_type(cls, param_name, value):
+    """Convert parameter's value to its type.
+
+    The intended use is to convert strings from HTTP request to the
+    appropriate parameter's type.
+    """
+    def to_bool(value):
+      if type(value) is bool:
+        return value
+      return {'True': True, 'False': False}.get(value, False)
+
+    def to_str(value):
+      return str(value)
+
+    cast = {
+        'enable_ts_monitoring': to_bool,
+    }.get(param_name, to_str)
+    return cast(value)
+
 
 def settings(fresh=False):
   """Loads GlobalConfig or a default one if not present.