Implement support for a Context parameter in image filters

gm/imagefiltersbase.cpp

Index: gm/imagefiltersbase.cpp
diff --git a/gm/imagefiltersbase.cpp b/gm/imagefiltersbase.cpp
index 86a7f81b47ab86fa9ec1bb9ee0ad877b527fae0f..b31fbebe605e63b84747cb013fc7bf887a585a77 100644
--- a/gm/imagefiltersbase.cpp
+++ b/gm/imagefiltersbase.cpp
@@ -25,7 +25,7 @@ public:
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(FailImageFilter)
 protected:
     FailImageFilter() : INHERITED(0) {}
-    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
+    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const Context&,
                                SkBitmap* result, SkIPoint* offset) const {
         return false;
     }
@@ -51,7 +51,7 @@ public:
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(IdentityImageFilter)
 protected:
     IdentityImageFilter() : INHERITED(0) {}
-    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
+    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const Context&,
                                SkBitmap* result, SkIPoint* offset) const {
         *result = src;
         return true;