Revert of Checking for valid colorType, alphaType, colorSpace in SkCodec (patchset #2 id:100001 of https://codereview.chromium.org/2319293003/ )

Reason for revert:
Broken perf bots

Original issue's description:
> 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

TBR=scroggo@google.com,brianosman@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2328663002

1 files changed, 23 insertions, 4 deletions

diff --git a/src/codec/SkWebpCodec.cpp b/src/codec/SkWebpCodec.cpp
index e8b27b2178..0c3aa402bd 100644
--- a/src/codec/SkWebpCodec.cpp
+++ b/src/codec/SkWebpCodec.cpp
@@ -144,6 +144,25 @@ SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
                            streamDeleter.release(), demux.release(), std::move(data));
 }
 
+static bool webp_conversion_possible(const SkImageInfo& dst, const SkImageInfo& src,
+                                     SkColorSpaceXform* colorXform) {
+    if (!valid_alpha(dst.alphaType(), src.alphaType())) {
+        return false;
+    }
+
+    switch (dst.colorType()) {
+        case kRGBA_F16_SkColorType:
+            return nullptr != colorXform;
+        case kBGRA_8888_SkColorType:
+        case kRGBA_8888_SkColorType:
+            return true;
+        case kRGB_565_SkColorType:
+            return nullptr == colorXform && src.alphaType() == kOpaque_SkAlphaType;
+        default:
+            return false;
+    }
+}
+
 SkISize SkWebpCodec::onGetScaledDimensions(float desiredScale) const {
     SkISize dim = this->getInfo().dimensions();
     // SkCodec treats zero dimensional images as errors, so the minimum size
@@ -193,15 +212,15 @@ bool SkWebpCodec::onGetValidSubset(SkIRect* desiredSubset) const {
 SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
                                          const Options& options, SkPMColor*, int*,
                                          int* rowsDecodedPtr) {
-    if (!conversion_possible(dstInfo, this->getInfo())) {
-        return kInvalidConversion;
-    }
 
     std::unique_ptr<SkColorSpaceXform> colorXform = nullptr;
     if (needs_color_xform(dstInfo, this->getInfo())) {
         colorXform = SkColorSpaceXform::New(sk_ref_sp(this->getInfo().colorSpace()),
                                             sk_ref_sp(dstInfo.colorSpace()));
-        SkASSERT(colorXform);
+    }
+
+    if (!webp_conversion_possible(dstInfo, this->getInfo(), colorXform.get())) {
+        return kInvalidConversion;
     }
 
     WebPDecoderConfig config;