Remove SkMemoryStream::peek()

Remove SkMemoryStream::peek()

I'd like to add a new API to SkStream for peeking - i.e. reading some
bytes without advancing the stream. This will be implemented for the
streams where it makes sense. I think the function should look
something like the following:

size_t peek(void* buffer, size_t bytesToRead) {
     return this->onPeek(buffer, bytesToRead);
}

virtual size_t onPeek(void* buffer, size_t bytesToRead) {
    return 0;   // unimplemented base class.
}

In order to avoid confusion, I'd like to remove SkMemoryStream::peek(),
which is not currently used internally, by Chrome, or by Android as far
as I can tell. There is also another function does the same thing:
getPosition().

BUG=skia:3257
Committed: https://skia.googlesource.com/skia/+/5cffba8d8e6965b10017fae7d8b67c8724e12822

[scroggo, 2015-03-27 19:32:15]

scroggo@google.com changed reviewers:
+ bungeman@google.com, djsollen@google.com, reed@google.com

[reed1, 2015-03-27 20:14:54]

+1 for removing unused APIs -- api lgtm

[scroggo, 2015-03-27 20:22:33]

The CQ bit was checked by scroggo@google.com

[commit-bot: I haz the power, 2015-03-27 20:22:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1039373002/1

[commit-bot: I haz the power, 2015-03-27 20:27:56]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/5cffba8d8e6965b10017fae7d8b67c8724e12822