Accept displacement with no displacement input

gm/displacement.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 "gm.h"
 #include "SkDisplacementMapEffect.h"
 #include "SkBitmapSource.h"
@@ skipping 165 matching lines @@
             (SkDisplacementMapEffect::kG_ChannelSelectorType,
              SkDisplacementMapEffect::kA_ChannelSelectorType,
              40.0f, displ, NULL, &cropRect)))->unref();
         drawClippedBitmap(canvas, 300, 300, paint);
         paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
             (SkDisplacementMapEffect::kR_ChannelSelectorType,
              SkDisplacementMapEffect::kA_ChannelSelectorType,
              40.0f, displ, NULL, &cropRect)))->unref();
         drawClippedBitmap(canvas, 400, 300, paint);
 
+        // Tests for images of different sizes
         displ.reset(SkNEW_ARGS(SkBitmapSource, (fSmall)));
         paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
             (SkDisplacementMapEffect::kR_ChannelSelectorType,
              SkDisplacementMapEffect::kG_ChannelSelectorType,
              40.0f, displ)))->unref();
         drawClippedBitmap(canvas, 0, 400, paint);
         displ.reset(SkNEW_ARGS(SkBitmapSource, (fLarge)));
         paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
             (SkDisplacementMapEffect::kB_ChannelSelectorType,
              SkDisplacementMapEffect::kA_ChannelSelectorType,
              40.0f, displ)))->unref();
         drawClippedBitmap(canvas, 100, 400, paint);
         displ.reset(SkNEW_ARGS(SkBitmapSource, (fLargeW)));
         paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
             (SkDisplacementMapEffect::kR_ChannelSelectorType,
              SkDisplacementMapEffect::kB_ChannelSelectorType,
              40.0f, displ)))->unref();
         drawClippedBitmap(canvas, 200, 400, paint);
         displ.reset(SkNEW_ARGS(SkBitmapSource, (fLargeH)));
         paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
             (SkDisplacementMapEffect::kG_ChannelSelectorType,
              SkDisplacementMapEffect::kA_ChannelSelectorType,
              40.0f, displ)))->unref();
         drawClippedBitmap(canvas, 300, 400, paint);
+
+        // Test for no given displacement input. In this case, both displacement
+        // and color should use the same bitmap, given to SkCanvas::drawBitmap()
+        // as an input argument.
+        paint.setImageFilter(SkNEW_ARGS(SkDisplacementMapEffect,
+            (SkDisplacementMapEffect::kG_ChannelSelectorType,
+             SkDisplacementMapEffect::kA_ChannelSelectorType,
+             40.0f, NULL)))->unref();
+        drawClippedBitmap(canvas, 400, 400, paint);
     }
 
 private:
     typedef GM INHERITED;
     SkBitmap fBitmap, fCheckerboard, fSmall, fLarge, fLargeW, fLargeH;
     bool fInitialized;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static GM* MyFactory(void*) { return new DisplacementMapGM; }
 static GMRegistry reg(MyFactory);
 
 }