Assert that F16 is always treated as linear in SkColorSpaceXform

src/core/SkColorSpaceXform.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorPriv.h"
 #include "SkColorSpace_Base.h"
 #include "SkColorSpacePriv.h"
@@ skipping 1097 matching lines @@
     build_gamma_tables(fSrcGammaTables, fSrcGammaTableStorage, 256, srcSpace, kToLinear);
     build_gamma_tables(fDstGammaTables, fDstGammaTableStorage, kDstGammaTableSize, dstSpace,
                        kFromLinear);
 }
 
 template <SkGammaNamed kDst, ColorSpaceMatch kCSM>
 void SkColorSpaceXform_Base<kDst, kCSM>
 ::apply(void* dst, const uint32_t* src, int len, SkColorType dstColorType, SkAlphaType dstAlphaType)
 const
 {
+    // F16 is always treated as linear.
+    SkASSERT(kRGBA_F16_SkColorType != dstColorType || kLinear_SkGammaNamed == kDst);
+
     if (kFull_ColorSpaceMatch == kCSM) {
         switch (dstAlphaType) {
             case kPremul_SkAlphaType:
                 // We can't skip the xform since we need to perform a premultiply in the
                 // linear space.
                 break;
             default:
                 switch (dstColorType) {
                     case kRGBA_8888_SkColorType:
                         return (void) memcpy(dst, src, len * sizeof(uint32_t));
@@ skipping 76 matching lines @@
             SkASSERT(false);
             return;
     }
 }
 
 std::unique_ptr<SkColorSpaceXform> SlowIdentityXform(const sk_sp<SkColorSpace>& space) {
         return std::unique_ptr<SkColorSpaceXform>(new SkColorSpaceXform_Base
                 <kNonStandard_SkGammaNamed, kNone_ColorSpaceMatch>
                 (space, SkMatrix::I(), space));
 }