Empty implementations for SkImageDecoder.

Add constructor and destructor, so SkScaledBitmapSampler's
DummyDecoder has no unresolved symbols in Chrome.

Fixes our Chrome canary.

Unreviewed.

Review URL: https://codereview.chromium.org/25536004

git-svn-id: http://skia.googlecode.com/svn/trunk@11566 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed