Several Dart bugs I encountered

I refactored the codes so that new implicit delayed UI component initialization can be used.
And I found a few restriction and bugs of Dart.

1. I needed to define default constructor without taking optional values. this is required to create UI component object without taking any parameters, in particular, parent value can not be passed at the property declaration time.
   So I first tried to use optional parameter '{}', but when I combined with Monitor suing Mixen, I found it does not allow to use mixin with a class in which the default constructor has optional parameters.
   
2. So I first try to avoid changing existing constructors(although it was not bad idea to change so, but it needed more changes), I moved Monitor class to be used as super class of the top level Component class. Then what I saw during execution was very strange problem. There was annotation class called Monitored, and reflection will get the instance through metadata, and in order to identify proper annotation class, it uses 'is" operator.
   What happened was that 'obj is Monitored' was not true even obj's runtimeType is Monitored!
   This kind of things happen in Java when different class loaders are used to instantiate an object, but in Dart, we will not manipulate class loading, so quite strange. So I basically abandoned this approach, and took the mixin approach again.(this was OK, since this approach would be more narrowly scoped, and appropriate for the purpose).
   
3. after all required changes are finished, and could run properly with DartVM mode, I tested this app with static mirror library which are to be used for javascript mode.
   If I run this with Dart VM, it run properly, but if we use javascript mode, the dart2js compiler crashed.
   Actually the message of the compiler problem was the same as a bug I reported before, and it was quickly fixed(but  I did not verify it for myself.) So I thought this would be fixed if I update the dart sdk(r28355) since the fixed version was older that that revision.
   But I found it was not fixed. Actually there were some workaround to fix previous problem using variable instead of direct type value, but this issue was not fixed by this workaround. So this may indeed be another bug.
   
4. Another problem I faced was the getting ClasssMirror of generic type. In order to provide javascript mode, portal mirror need to provide basic reflection features from concrete classes.
   For instance it need to use generic type's type(Type). right now, in order to have right type value, namely the type where parameters are substituted is only to go through instantiating the object.
   but new implicit delayed UI component initialization will call reflection library when  the default constructor is called. So this introduced infinite loop. Actually these kind of problems were I anticipated when I knew the current  way to get Type. Essentially this is very dirty trick. Also some case, this will case unnecessary resource usage as well. I avoided this problem using dirty trick to use static variable not to call the sub component initialization(although the global variable is defined as private, so it is not so bad way..).
   
5. This issue also made clear the current constructor has a lot of restriction, lack of flexibility. The simple way to avoid this in Java was to define another constructor to take such flag to disable calling sub component initialization. But in Dart, if we define one constructor, there is no other way to define another.   So I was forced to use global variable.