Revert of Add SkPngChunkReader. (patchset #9 id:160001 of https://codereview.chromium...

Revert of Add SkPngChunkReader. (patchset #9 id:160001 of https://codereview.chromium.org/1040453002/ )

Reason for revert:
Busted Chromium builds:

../../third_party/skia/src/ports/SkImageDecoder_empty.cpp:63:17: error: no type
named 'Peeker' in 'SkImageDecoder'
SkImageDecoder::Peeker* SkImageDecoder::setPeeker(Peeker*) {
~~~~~~~~~~~~~~~~^
../../third_party/skia/src/ports/SkImageDecoder_empty.cpp:63:51: error: unknown
type name 'Peeker'
SkImageDecoder::Peeker* SkImageDecoder::setPeeker(Peeker*) {

Original issue's description:
> Add SkPngChunkReader.
>
> This class allows a client of SkCodec to read chunks in the data
> stream that are not recognized by libpng. This is used by Android
> to specify ninepatch data.
>
> Taken from SkImageDecoder::Peeker. Modify the name of the class
> and its method to be more specific to their use. Make
> SkImageDecoder::Peeker a subclass of the new class, to help stage
> the change in Android.
>
> Add a test to verify that it works.
>
> BUG=skia:4574
> BUG=skia:3257
>
> Committed: https://skia.googlesource.com/skia/+/3389e00136188800b98ca69488c0418c374fd78b

TBR=djsollen@google.com,reed@google.com,msarett@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4574

Review URL: https://codereview.chromium.org/1472863003