Add documention on SkBlitter for runs, and small cleanups.

src/core/SkBlitter.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 "SkBlitter.h"
 #include "SkAntiRun.h"
 #include "SkColor.h"
@@ skipping 140 matching lines @@
             while (--height >= 0) {
                 int affectedRightBit = mask.fBounds.width() - 1;
                 ptrdiff_t rowBytes = (affectedRightBit >> 3) + 1;
                 SkASSERT(bits + rowBytes <= endOfImage);
                 U8CPU rightMask = generate_right_mask((affectedRightBit & 7) + 1);
                 bits_to_runs(this, cx, cy, bits, 0xFF, rowBytes, rightMask);
                 bits += maskRowBytes;
                 cy += 1;
             }
         } else {
-            // Bits is calculated as the offset into the mask at the point {cx, cy} therfore, all
+            // Bits is calculated as the offset into the mask at the point {cx, cy} therefore, all
             // addressing into the bit mask is relative to that point. Since this is an address
             // calculated from a arbitrary bit in that byte, calculate the left most bit.
             int bitsLeft = cx - ((cx - maskLeft) & 7);
 
             // Everything is relative to the bitsLeft.
             int leftEdge = cx - bitsLeft;
             SkASSERT(leftEdge >= 0);
             int rightEdge = clip.fRight - bitsLeft;
             SkASSERT(rightEdge > leftEdge);
 
@@ skipping 833 matching lines @@
     fShaderContext->~Context();
     SkShader::Context* ctx = fShader->createContext(rec, (void*)fShaderContext);
     if (nullptr == ctx) {
         // Need a valid context in fShaderContext's storage, so we can later (or our caller) call
         // the in-place destructor.
         new (fShaderContext) SkZeroShaderContext(*fShader, rec);
         return false;
     }
     return true;
 }