Accept displacement with no displacement input

src/effects/SkDisplacementMapEffect.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDisplacementMapEffect.h"
 #include "SkFlattenableBuffers.h"
 #include "SkUnPreMultiply.h"
@@ skipping 165 matching lines @@
     buffer.writeInt((int) fXChannelSelector);
     buffer.writeInt((int) fYChannelSelector);
     buffer.writeScalar(fScale);
 }
 
 bool SkDisplacementMapEffect::onFilterImage(Proxy* proxy,
                                             const SkBitmap& src,
                                             const SkMatrix& ctm,
                                             SkBitmap* dst,
                                             SkIPoint* offset) {
-    SkBitmap displ, color = src;
+    SkBitmap displ = src, color = src;
     SkImageFilter* colorInput = getColorInput();
     SkImageFilter* displacementInput = getDisplacementInput();
-    SkASSERT(NULL != displacementInput);
     if ((colorInput && !colorInput->filterImage(proxy, src, ctm, &color, offset)) ||
-        !displacementInput || !displacementInput->filterImage(proxy, src, ctm, &displ, offset)) {
+        (displacementInput && !displacementInput->filterImage(proxy, src, ctm, &displ, offset))) {
         return false;
     }
     if ((displ.config() != SkBitmap::kARGB_8888_Config) ||
         (color.config() != SkBitmap::kARGB_8888_Config)) {
         return false;
     }
 
     SkAutoLockPixels alp_displacement(displ), alp_color(color);
     if (!displ.getPixels() || !color.getPixels()) {
         return false;
@@ skipping 338 matching lines @@
                                                         const GrGLCaps&) {
     const GrDisplacementMapEffect& displacementMap =
         drawEffect.castEffect<GrDisplacementMapEffect>();
 
     EffectKey xKey = displacementMap.xChannelSelector();
     EffectKey yKey = displacementMap.yChannelSelector() << SkDisplacementMapEffect::kKeyBits;
 
     return xKey | yKey;
 }
 #endif