Graphical output has "padded" data when pipelining in a non matching texture size


## *What* is wrong?

When pipelining in another kernel with a different size to the kernel that is marked graphical, the canvas becomes bigger by the same factor.

## *Where* does it happen?

In the browser.

## *How* do we replicate the issue?

https://codesandbox.io/s/lucid-wilson-5eb3d

```javascript
let kernalA = gpu.createKernel(
function () {
return this.thread.x / 100;
},
{
output: [100, 100, 10],
pipeline: true
}
);

let kernalB = gpu.createKernel(
function (pars) {
this.color(pars[0][this.thread.y][this.thread.x], 0, 0);
},
{
output: [100, 100],
graphical: true
}
);

kernalB(kernalA());

```

## *How* important is this (1-5)?

6(9)

## Expected behavior (i.e. solution)

The dimensions of the canvas should match the output of the kernel marked as graphical.

## Other Comments