Move SkComposeImageFilter into its own {.h, .cpp} files

include/effects/SkTestImageFilters.h

 #ifndef _SkTestImageFilters_h
 #define _SkTestImageFilters_h
 
 #include "SkImageFilter.h"
 #include "SkPoint.h"
 
-class SK_API SkComposeImageFilter : public SkImageFilter {
-public:
-    SkComposeImageFilter(SkImageFilter* outer, SkImageFilter* inner) : INHERITED(outer, inner) {}
-    virtual ~SkComposeImageFilter();
-
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkComposeImageFilter)
-
-protected:
-    SkComposeImageFilter(SkFlattenableReadBuffer& buffer);
-
-    virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
-                               SkBitmap* result, SkIPoint* loc) SK_OVERRIDE;
-    virtual bool onFilterBounds(const SkIRect&, const SkMatrix&, SkIRect*) SK_OVERRIDE;
-
-private:
-    typedef SkImageFilter INHERITED;
-};
-
-///////////////////////////////////////////////////////////////////////////////
-
 // Fun mode that scales down (only) and then scales back up to look pixelated
 class SK_API SkDownSampleImageFilter : public SkImageFilter {
 public:
     SkDownSampleImageFilter(SkScalar scale) : INHERITED(0), fScale(scale) {}
 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkDownSampleImageFilter)
 
 protected:
     SkDownSampleImageFilter(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
                                SkBitmap* result, SkIPoint* loc) SK_OVERRIDE;
 
 private:
     SkScalar fScale;
 
     typedef SkImageFilter INHERITED;
 };
 
 #endif