Add documention on SkBlitter for runs, and small cleanups.

src/core/SkBlitter_ARGB32.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 "SkCoreBlitters.h"
 #include "SkColorPriv.h"
 #include "SkShader.h"
@@ skipping 156 matching lines @@
     SkASSERT(fSrcA != 0xFF);
 
     if (fSrcA == 0) {
         return;
     }
 
     if (SkBlitMask::BlitColor(fDevice, mask, clip, fColor)) {
         return;
     }
 
-    if (mask.fFormat == SkMask::kBW_Format) {
-        SkARGB32_BlendBW(fDevice, mask, clip, fPMColor, SkAlpha255To256(255 - fSrcA));
-    } else if (SkMask::kARGB32_Format == mask.fFormat) {
-        SkARGB32_Blit32(fDevice, mask, clip, fPMColor);
+    switch (mask.fFormat) {
+        case SkMask::kBW_Format:
+            SkARGB32_BlendBW(fDevice, mask, clip, fPMColor, SkAlpha255To256(255 - fSrcA));
+            break;
+        case SkMask::kARGB32_Format:
+            SkARGB32_Blit32(fDevice, mask, clip, fPMColor);
+            break;
+        default:
+            SkFAIL("Mask format not handled.");
     }
 }
 
 void SkARGB32_Opaque_Blitter::blitMask(const SkMask& mask,
                                        const SkIRect& clip) {
     SkASSERT(mask.fBounds.contains(clip));
 
     if (SkBlitMask::BlitColor(fDevice, mask, clip, fColor)) {
         return;
     }
 
-    if (mask.fFormat == SkMask::kBW_Format) {
-        SkARGB32_BlitBW(fDevice, mask, clip, fPMColor);
-    } else if (SkMask::kARGB32_Format == mask.fFormat) {
-        SkARGB32_Blit32(fDevice, mask, clip, fPMColor);
+    switch (mask.fFormat) {
+        case SkMask::kBW_Format:
+            SkARGB32_BlitBW(fDevice, mask, clip, fPMColor);
+            break;
+        case SkMask::kARGB32_Format:
+            SkARGB32_Blit32(fDevice, mask, clip, fPMColor);
+            break;
+        default:
+            SkFAIL("Mask format not handled.");
     }
 }
 
 void SkARGB32_Opaque_Blitter::blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) {
     uint32_t* device = fDevice.writable_addr32(x, y);
     SkDEBUGCODE((void)fDevice.writable_addr32(x + 1, y);)
 
     device[0] = SkFastFourByteInterp(fPMColor, device[0], a0);
     device[1] = SkFastFourByteInterp(fPMColor, device[1], a1);
 }
@@ skipping 470 matching lines @@
             SkBlitRow::Proc32 proc = (255 == alpha) ? fProc32 : fProc32Blend;
             do {
                 shaderContext->shadeSpan(x, y, span, 1);
                 proc(device, span, 1, alpha);
                 y += 1;
                 device = (uint32_t*)((char*)device + deviceRB);
             } while (--height > 0);
         }
     }
 }