Issue 4497. Show the best known type in the text hover.

Issue 4497. Show the best known type in the text hover.
https://code.google.com/p/dart/issues/detail?id=4497

R=brianwilkerson@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=30648

[Brian Wilkerson, 2013-11-25 16:26:54]

Assuming this is what we want to do, LGTM.

I'm not a UX person, but I wonder whether we might want to show both the static
*and* propagated type information. Something along the lines of "this is the
variable x defined to be of type 'num', but which we believe to have a type of
'int' at this point". The reason I ask is that I think it might be confusing to
have the "type" of a variable change throughout the method (or even just to be
different than the declared type). Might be worth asking Luke about it if he
hasn't already weighed in.

[scheglov, 2013-11-25 22:12:50]

Committed patchset #1 manually as r30648 (presubmit successful).