Remove external matrix feature.

Remove external matrix feature.

We haven't been testing this for nearly two years.

R=reed@google.com
Committed: https://code.google.com/p/skia/source/detail?r=5857

[reed1, 2012-10-08 20:40:26]

lgtm

    if (hasCustomD1GProc(*draw)) {
        // todo: fix this assumption about clips w/ custom
        fClip = draw->fClip;
        fClipBounds = fClip->getBounds();
        return draw->fProcs->fD1GProc;
    }

What the heck is that check?