Int64 tweaks for better type infererence

Int64 tweaks for better type infererence

In some programs Int64._l was inferred as possibly null.

BUG=
R=herhut@google.com

Committed: https://code.google.com/p/dart/source/detail?r=43998

[sra1, 2015-02-23 00:43:38]

sra@google.com changed reviewers:
+ herhut@google.com

[sra1, 2015-02-23 00:43:39]

I'm not sure why Int64._l was inferred as [null|subtype=int]
Int64.toInt() was also inferred as [null|subtype=int].

It may have been related to there being a definition of noSuchMethod, so I moved
more masking constants to the receiver position.

[sra1, 2015-02-24 04:16:53]

ping

[herhut, 2015-02-24 19:04:59]

On 2015/02/24 04:16:53, sra1 wrote:
> ping

Did you try this before or after https://codereview.chromium.org/941293002/
landed? I recently changed type propagation such that it only applied if the
left hand side is a primitive and one of them is a uint31. Maybe subtype|int is
not considered a primitive. 

I will take a look why this does not work but independently of that, this change
is a good idea.

LGTM

[sra1, 2015-02-24 20:52:06]

Committed patchset #1 (id:1) manually as 43998 (presubmit successful).