fix use of uninitialized flag in SkCodec

SkCodec class has the fStartedIncrementalDecode field, which is not
initialized on construction, but may be used in incrementalDecode
method being uninitialized.

Bug: skia:
Change-Id: I378412a375100ad2df4aa38f2dd5682867e0e34b
Reviewed-on: https://skia-review.googlesource.com/53160
Commit-Queue: Heather Miller <hcm@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
2 files changed