Fixed warning causing drone.io to fail

Fixed warning causing drone.io to fail

BUG=

[Jennifer Messerly, 2013-08-16 17:47:27]

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
eek, this is ugly!
can you add a TODO and refer to this bug:
https://code.google.com/p/dart/issues/detail?id=6111

[terry, 2013-08-16 17:55:34]

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
Do you think another solution is to change the signature of js.dart context
getter from

Proxy get context

to

get context

So it's untyped?  Wouldn't that solve this particular problem.

On 2013/08/16 17:47:27, John Messerly wrote:
> eek, this is ugly!
> can you add a TODO and refer to this bug:
> https://code.google.com/p/dart/issues/detail?id=6111
>

[Jennifer Messerly, 2013-08-16 17:58:32]

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
On 2013/08/16 17:55:34, terry wrote:
> Do you think another solution is to change the signature of js.dart context
> getter from
> 
> Proxy get context
> 
> to
> 
> get context
> 
> So it's untyped?  Wouldn't that solve this particular problem.
> 
> On 2013/08/16 17:47:27, John Messerly wrote:
> > eek, this is ugly!
> > can you add a TODO and refer to this bug:
> > https://code.google.com/p/dart/issues/detail?id=6111
> >  
> 

in this case, yes. but it doesn't help with the general problem

[Siggi Cherem (dart-lang), 2013-08-16 18:13:06]

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
On 2013/08/16 17:58:32, John Messerly wrote:
> On 2013/08/16 17:55:34, terry wrote:
> > Do you think another solution is to change the signature of js.dart context
> > getter from
> > 
> > Proxy get context
> > 
> > to
> > 
> > get context
> > 
> > So it's untyped?  Wouldn't that solve this particular problem.
> > 
> > On 2013/08/16 17:47:27, John Messerly wrote:
> > > eek, this is ugly!
> > > can you add a TODO and refer to this bug:
> > > https://code.google.com/p/dart/issues/detail?id=6111
> > >  
> > 
> 
> in this case, yes. but it doesn't help with the general problem

I believe you can also fix this by using this notation:

js.context["Platform"];

[Jennifer Messerly, 2013-08-16 18:17:56]

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
On 2013/08/16 18:13:06, Siggi Cherem (dart-lang) wrote:
> On 2013/08/16 17:58:32, John Messerly wrote:
> > On 2013/08/16 17:55:34, terry wrote:
> > > Do you think another solution is to change the signature of js.dart
context
> > > getter from
> > > 
> > > Proxy get context
> > > 
> > > to
> > > 
> > > get context
> > > 
> > > So it's untyped?  Wouldn't that solve this particular problem.
> > > 
> > > On 2013/08/16 17:47:27, John Messerly wrote:
> > > > eek, this is ugly!
> > > > can you add a TODO and refer to this bug:
> > > > https://code.google.com/p/dart/issues/detail?id=6111
> > > >  
> > > 
> > 
> > in this case, yes. but it doesn't help with the general problem
> 
> I believe you can also fix this by using this notation:
> 
> js.context["Platform"];

Yeah, the strange thing about that though is we are using dot notation later on
when we use platform, so it seems inconsistent.

Another workaround is:

    var context = js.context;
    var platform = context.Platform;

[terry, 2013-08-16 19:02:05]

Added TODO

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.dart
File lib/polymer_element.dart (right):

https://chromiumcodereview.appspot.com/23095010/diff/1/lib/polymer_element.da...
lib/polymer_element.dart:177: var platform = (js.context as dynamic).Platform;
Done.

My larger question is the TODO should go in js.dart with a temporary fix for the
context getter.  Then all downstream users of js interop aren't hitting this
ugliness.

On 2013/08/16 17:58:32, John Messerly wrote:
> On 2013/08/16 17:55:34, terry wrote:
> > Do you think another solution is to change the signature of js.dart context
> > getter from
> > 
> > Proxy get context
> > 
> > to
> > 
> > get context
> > 
> > So it's untyped?  Wouldn't that solve this particular problem.
> > 
> > On 2013/08/16 17:47:27, John Messerly wrote:
> > > eek, this is ugly!
> > > can you add a TODO and refer to this bug:
> > > https://code.google.com/p/dart/issues/detail?id=6111
> > >  
> > 
> 
> in this case, yes. but it doesn't help with the general problem