Fix bug in erosion filtering

src/effects/SkMorphologyImageFilter.cpp

 /*
  * Copyright 2012 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 "SkMorphologyImageFilter.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 489 matching lines @@
     desc.fConfig = kSkia8888_GrPixelConfig;
     SkIRect srcRect = rect;
 
     if (radius.fWidth > 0) {
         GrAutoScratchTexture ast(context, desc);
         GrContext::AutoRenderTarget art(context, ast.texture()->asRenderTarget());
         apply_morphology_pass(context, src, srcRect, dstRect, radius.fWidth,
                               morphType, Gr1DKernelEffect::kX_Direction);
         SkIRect clearRect = SkIRect::MakeXYWH(dstRect.fLeft, dstRect.fBottom,
                                               dstRect.width(), radius.fHeight);
-        context->clear(&clearRect, 0x0);
+        context->clear(&clearRect, GrMorphologyEffect::kErode_MorphologyType == morphType ? 
+                                   SK_ColorWHITE : 
+                                   SK_ColorTRANSPARENT);
         src.reset(ast.detach());
         srcRect = dstRect;
     }
     if (radius.fHeight > 0) {
         GrAutoScratchTexture ast(context, desc);
         GrContext::AutoRenderTarget art(context, ast.texture()->asRenderTarget());
         apply_morphology_pass(context, src, srcRect, dstRect, radius.fHeight,
                               morphType, Gr1DKernelEffect::kY_Direction);
         src.reset(ast.detach());
     }
@@ skipping 62 matching lines @@
 
     if (!apply_morphology(input, bounds, GrMorphologyEffect::kErode_MorphologyType, radius(), result)) {
         return false;
     }
     offset->fX += bounds.left();
     offset->fY += bounds.top();
     return true;
 }
 
 #endif