Rename SkCodec::kNone to SkCodec::kNoFrame

Add a SK_LEGACY_SKCODEC_NONE_ENUM #define'able to ease transition.

Also rename another internal "kNone" enum in SkWebpCodec.cpp.

The "kNone" name is overloaded:
- include/core/SkImageGenerator.h defines its own kNone.
- include/encode/SkPngEncoder.h defines its own kNone.
- include/private/GrTypesPriv.h defines multiple kNone's.

Bug: skia:
Change-Id: I18c03a74f2f1b0237016e0eef53dcd4478b82609
Reviewed-on: https://skia-review.googlesource.com/146020
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
diff --git a/gm/animatedGif.cpp b/gm/animatedGif.cpp
index 8b92e94..6e9789e 100644
--- a/gm/animatedGif.cpp
+++ b/gm/animatedGif.cpp
@@ -54,7 +54,7 @@
             SkCodec::Options opts;
             opts.fFrameIndex = frameIndex;
             const int requiredFrame = fFrameInfos[frameIndex].fRequiredFrame;
-            if (requiredFrame != SkCodec::kNone) {
+            if (requiredFrame != SkCodec::kNoFrame) {
                 SkASSERT(requiredFrame >= 0
                          && static_cast<size_t>(requiredFrame) < fFrames.size());
                 SkBitmap& requiredBitmap = fFrames[requiredFrame];