Checking for valid colorType, alphaType, colorSpace in SkCodec

* Refactor to share code between SkPngCodec and SkWebpCodec
* Didn't end up sharing with SkJpegCodec but did refactor
  that code a bit
* Disallow conversions to F16 with non-linear color spaces
* Fail to decode if we fail to create a SkColorSpaceXform
  (should be an assert soon).  We used to fallback on a
  legacy decode if we failed to create the transform.
* A bunch of name changes

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2319293003

Committed: https://skia.googlesource.com/skia/+/7a9900d6d34e437bb24beb5524a1f6488ae138c9
Review-Url: https://codereview.chromium.org/2319293003
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index caf6f52..fcc4a33 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -896,6 +896,9 @@
     if (kUnpremul_SkAlphaType == decodeInfo.alphaType()) {
         decodeInfo = decodeInfo.makeAlphaType(kPremul_SkAlphaType);
     }
+    if (kRGBA_F16_SkColorType == fColorType) {
+        decodeInfo = decodeInfo.makeColorSpace(decodeInfo.colorSpace()->makeLinearGamma());
+    }
 
     SkImageInfo bitmapInfo = decodeInfo;
     if (kRGBA_8888_SkColorType == decodeInfo.colorType() ||