Make SkImageFilter methods const.

include/effects/SkDisplacementMapEffect.h

Index: include/effects/SkDisplacementMapEffect.h
diff --git a/include/effects/SkDisplacementMapEffect.h b/include/effects/SkDisplacementMapEffect.h
index de07fe4ca4c3f1a9cc50f1c10b52d0d13c519e7b..5de4814951a6afb0f299ed90a1db9bf24b8e3e5c 100644
--- a/include/effects/SkDisplacementMapEffect.h
+++ b/include/effects/SkDisplacementMapEffect.h
@@ -36,7 +36,7 @@ public:
                                const SkBitmap& src,
                                const SkMatrix& ctm,
                                SkBitmap* dst,
-                               SkIPoint* offset) SK_OVERRIDE;
+                               SkIPoint* offset) const SK_OVERRIDE;
     virtual void computeFastBounds(const SkRect& src, SkRect* dst) const SK_OVERRIDE;
 
     virtual bool onFilterBounds(const SkIRect& src, const SkMatrix&,
@@ -45,7 +45,7 @@ public:
 #if SK_SUPPORT_GPU
     virtual bool canFilterImageGPU() const SK_OVERRIDE { return true; }
     virtual bool filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
-                                SkBitmap* result, SkIPoint* offset) SK_OVERRIDE;
+                                SkBitmap* result, SkIPoint* offset) const SK_OVERRIDE;
 #endif
 
 protected:
@@ -57,8 +57,6 @@ private:
     ChannelSelectorType fYChannelSelector;
     SkScalar fScale;
     typedef SkImageFilter INHERITED;
-    SkImageFilter* getDisplacementInput() { return getInput(0); }
-    SkImageFilter* getColorInput() { return getInput(1); }
     const SkImageFilter* getDisplacementInput() const { return getInput(0); }
     const SkImageFilter* getColorInput() const { return getInput(1); }
 };