use Uint8ClampedArray in canvas ImageData
use Uint8ClampedArray in canvas ImageData

Summary:
I was having a problem with data field in ImageData class because its defined as `Array<number>` instead of `Uint8ClampedArray`. With `Array<number>` I can't use various methods defined on the typed array.

```
imageData.data.set(buffer);
               ^^^ property `set`. Property not found in
imageData.data.set(buffer);
^^^^^^^^^^^^^^^^^^^^^^^^^^ Array
```

reference: https://developer.mozilla.org/en-US/docs/Web/API/ImageData
Closes https://github.com/facebook/flow/pull/2068

Reviewed By: bhosmer

Differential Revision: D3572162

Pulled By: avikchaudhuri

fbshipit-source-id: 0fbb20b0e593cd14c9dd7ca7cf8d05583bd5cbac

claudiopro/flow,gabro/flow,samwgoldman/flow,fletcherw/flow,gabro/flow,gabelevi/flow,gabro/flow,JonathanUsername/flow,JonathanUsername/flow,MichaelDeBoey/flow,popham/flow,chenglou/flow,ForbesLindesay/flow,claudiopro/flow,gabro/flow,samwgoldman/flow,JonathanUsername/flow,JonathanUsername/flow,MichaelDeBoey/flow,gabelevi/flow,AprilArcus/flow,TiddoLangerak/flow,jamesgpearce/flow,jeffmo/flow,nmote/flow,chenglou/flow,facebook/flow,TiddoLangerak/flow,ylu1317/flow,jamesgpearce/flow,chenglou/flow,TiddoLangerak/flow,mroch/flow,fletcherw/flow,jgrund/flow,jamesgpearce/flow,AgentME/flow,mroch/flow,JonathanUsername/flow,MichaelDeBoey/flow,ForbesLindesay/flow,popham/flow,gabelevi/flow,AprilArcus/flow,gabelevi/flow,popham/flow,facebook/flow,jamesgpearce/flow,ForbesLindesay/flow,AgentME/flow,facebook/flow,fletcherw/flow,popham/flow,facebook/flow,jdelStrother/flow,popham/flow,samwgoldman/flow,jamesgpearce/flow,MichaelDeBoey/flow,ForbesLindesay/flow,ylu1317/flow,nmote/flow,facebook/flow,TiddoLangerak/flow,AprilArcus/flow,ylu1317/flow,mroch/flow,facebook/flow,gabelevi/flow,fletcherw/flow,chenglou/flow,nmote/flow,samwgoldman/flow,facebook/flow,jamesgpearce/flow,claudiopro/flow,AprilArcus/flow,samwgoldman/flow,jeffmo/flow,jamesgpearce/flow,ForbesLindesay/flow,claudiopro/flow,MichaelDeBoey/flow,jeffmo/flow,jdelStrother/flow,chenglou/flow,popham/flow,jdelStrother/flow,jdelStrother/flow,ForbesLindesay/flow,jgrund/flow,AgentME/flow,popham/flow,gabelevi/flow,jdelStrother/flow,JonathanUsername/flow,jeffmo/flow,nmote/flow,nmote/flow,jgrund/flow,chenglou/flow,fletcherw/flow,AprilArcus/flow,mroch/flow,gabro/flow,jgrund/flow,ylu1317/flow,jdelStrother/flow,JonathanUsername/flow,TiddoLangerak/flow,jeffmo/flow,claudiopro/flow,mroch/flow,AprilArcus/flow,samwgoldman/flow,fletcherw/flow,jeffmo/flow,mroch/flow,nmote/flow,nmote/flow,gabelevi/flow,ylu1317/flow,jgrund/flow,AgentME/flow,mroch/flow,AgentME/flow,samwgoldman/flow,gabro/flow,jgrund/flow