revert 2826, restore option for non-dithered gradients (used by chrome)



git-svn-id: http://skia.googlecode.com/svn/trunk@2836 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkGradientShader.cpp b/src/effects/SkGradientShader.cpp
index 0518686..bc7f8a3 100644
--- a/src/effects/SkGradientShader.cpp
+++ b/src/effects/SkGradientShader.cpp
@@ -1,3 +1,4 @@
+
 /*
  * Copyright 2006 The Android Open Source Project
  *
@@ -18,6 +19,10 @@
     #define SK_USE_FLOAT_SQRT
 #endif
 
+#ifndef SK_DISABLE_DITHER_32BIT_GRADIENT
+    #define USE_DITHER_32BIT_GRADIENT
+#endif
+
 static void sk_memset32_dither(uint32_t dst[], uint32_t v0, uint32_t v1,
                                int count) {
     if (count > 0) {
@@ -842,8 +847,13 @@
     SkMatrix::MapXYProc dstProc = fDstToIndexProc;
     TileProc            proc = fTileProc;
     const SkPMColor* SK_RESTRICT cache = this->getCache32();
+#ifdef USE_DITHER_32BIT_GRADIENT
     int                 toggle = ((x ^ y) & 1) << kCache32Bits;
     const int           TOGGLE_MASK = (1 << kCache32Bits);
+#else
+    int toggle = 0;
+    const int TOGGLE_MASK = 0;
+#endif
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         dstProc(fDstToIndex, SkIntToScalar(x) + SK_ScalarHalf,