Revert "share constructors/enum in both variants of SkReadBuffer"

This reverts commit 2ae333799178bf71fac5263522b8d570f3f3e4e8.

Reason for revert: broke google3

Original change's description:
> share constructors/enum in both variants of SkReadBuffer
> 
> Bug: skia:
> Change-Id: I5a90e1f9a9687df2dd2f69d96ac805bf244cec50
> Reviewed-on: https://skia-review.googlesource.com/c/179844
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Mike Reed <reed@google.com>
> Auto-Submit: Mike Reed <reed@google.com>

TBR=reed@google.com

Change-Id: I4735fe2336974240edab0eb7ef23f93d461c0bdf
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/179857
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed