[turbofan] Fix invalid access to Parameter index.

[turbofan] Fix invalid access to Parameter index.

A Parameter operator contains a ParameterInfo payload, not an int
payload, so the OpParameter<int> cast is invalid (and only worked by
coincidence currently).

BUG=chromium:515215
LOG=n
R=yangguo@chromium.org

Committed: https://crrev.com/efab0b74ddfe44ef03cad6822910f178a1055aaa
Cr-Commit-Position: refs/heads/master@{#29919}

[Benedikt Meurer, 2015-07-30 06:01:35]

Hey Yang,

Simple fix. Please take a look.

Thanks,
Benedikt

[Yang, 2015-07-30 06:03:19]

On 2015/07/30 06:01:35, Benedikt Meurer wrote:
> Hey Yang,
> 
> Simple fix. Please take a look.
> 
> Thanks,
> Benedikt

lgtm

[Benedikt Meurer, 2015-07-30 06:28:11]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-07-30 06:28:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1266743002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1266743002/1

[commit-bot: I haz the power, 2015-07-30 09:16:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-30 09:16:37]

Patchset 1 (id:??) landed as
https://crrev.com/efab0b74ddfe44ef03cad6822910f178a1055aaa
Cr-Commit-Position: refs/heads/master@{#29919}