Add onIsEncoded to image decoders.

Add onIsEncoded to image decoders.

We want to be able to query whether an image is encoded or not from
within Skia. In order to do this, we are adding onIsEncoded() to the
image generators.

This is the second part of a 3-part patch.
The first is https://chromiumcodereview.appspot.com/2434323002/
The third is https://codereview.chromium.org/2337803002/

BUG=646089

[cblume, 2016-10-20 19:09:58]

cblume@chromium.org changed reviewers:
+ bsalomon@google.com, vmpstr@chromium.org

[cblume, 2016-10-20 19:09:59]

PTAL

This is the second part in the 3-part patches to add isEncoded to SkImage.

[cblume, 2016-10-21 07:57:54]

Given the update in https://skia-review.googlesource.com/c/3780/ I think this
patch is no longer needed. I'm closing it.

[cblume, 2016-10-21 07:58:03]

Description was changed from

==========
Add onIsEncoded to image decoders.

We want to be able to query whether an image is encoded or not from
within Skia. In order to do this, we are adding onIsEncoded() to the
image generators.

This is the second part of a 3-part patch.
The first is https://chromiumcodereview.appspot.com/2434323002/
The third is https://codereview.chromium.org/2337803002/

BUG=646089
==========

to

==========
Add onIsEncoded to image decoders.

We want to be able to query whether an image is encoded or not from
within Skia. In order to do this, we are adding onIsEncoded() to the
image generators.

This is the second part of a 3-part patch.
The first is https://chromiumcodereview.appspot.com/2434323002/
The third is https://codereview.chromium.org/2337803002/

BUG=646089
==========