Make SkBlitter hierarchy explicit about what needs to be implemented.

src/core/SkBlitter_Sprite.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkOpts.h"
 #include "SkSmallAllocator.h"
 #include "SkSpriteBlitter.h"
 
-SkSpriteBlitter::SkSpriteBlitter(const SkPixmap& source) : fSource(source) {}
+SkSpriteBlitter::SkSpriteBlitter(const SkPixmap& source)
+    : fSource(source) {}
 
 void SkSpriteBlitter::setup(const SkPixmap& dst, int left, int top, const SkPaint& paint) {
     fDst = dst;
     fLeft = left;
     fTop = top;
     fPaint = &paint;
 }
 
-#ifdef SK_DEBUG
 void SkSpriteBlitter::blitH(int x, int y, int width) {
     SkDEBUGFAIL("how did we get here?");
+
+    // Fallback to blitRect.
+    this->blitRect(x, y, width, 1);
 }
 
-void SkSpriteBlitter::blitAntiH(int x, int y, const SkAlpha antialias[],
-                                const int16_t runs[]) {
+void SkSpriteBlitter::blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]) {
     SkDEBUGFAIL("how did we get here?");
+
+    // No fallback strategy.
 }
 
 void SkSpriteBlitter::blitV(int x, int y, int height, SkAlpha alpha) {
     SkDEBUGFAIL("how did we get here?");
+
+    // Fall back to superclass if the code gets here in release mode.
+    INHERITED::blitV(x, y, height, alpha);
 }
 
-void SkSpriteBlitter::blitMask(const SkMask&, const SkIRect& clip) {
+void SkSpriteBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
     SkDEBUGFAIL("how did we get here?");
+
+    // Fall back to superclass if the code gets here in release mode.
+    INHERITED::blitMask(mask, clip);
 }
-#endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
 //  Only valid if...
 //      1. src == dst format
 //      2. paint has no modifiers (i.e. alpha, colorfilter, etc.)
 //      3. xfermode needs no blending: e.g. kSrc_Mode or kSrcOver_Mode + opaque src
 //
-class SkSpriteBlitter_Src_SrcOver : public SkSpriteBlitter {
+class SkSpriteBlitter_Src_SrcOver final : public SkSpriteBlitter {
 public:
     static bool Supports(const SkPixmap& dst, const SkPixmap& src, const SkPaint& paint) {
         if (dst.colorType() != src.colorType()) {
             return false;
         }
         if (dst.info().profileType() != src.info().profileType()) {
             return false;
         }
         if (paint.getMaskFilter() || paint.getColorFilter() || paint.getImageFilter()) {
             return false;
@@ skipping 15 matching lines @@
         // At this point memcpy can't be used. The following check for using SrcOver.
 
         if (dst.colorType() != kN32_SkColorType
             || dst.info().profileType() != kSRGB_SkColorProfileType) {
             return false;
         }
 
         return SkXfermode::kSrcOver_Mode == mode;
     }
 
-    SkSpriteBlitter_Src_SrcOver(const SkPixmap& src)  : INHERITED(src) {}
+    SkSpriteBlitter_Src_SrcOver(const SkPixmap& src)
+        : INHERITED(src) {}
 
     void setup(const SkPixmap& dst, int left, int top, const SkPaint& paint) override {
         SkASSERT(Supports(dst, fSource, paint));
         this->INHERITED::setup(dst, left, top, paint);
         SkXfermode::Mode mode;
         if (!SkXfermode::AsMode(paint.getXfermode(), &mode)) {
             SkFAIL("Should never happen.");
         }
 
         SkASSERT(mode == SkXfermode::kSrcOver_Mode || mode == SkXfermode::kSrc_Mode);
@@ skipping 83 matching lines @@
             default:
                 break;
         }
     }
 
     if (blitter) {
         blitter->setup(dst, left, top, paint);
     }
     return blitter;
 }