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

include/effects/SkComposeImageFilter.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkComposeImageFilter_DEFINED
+#define SkComposeImageFilter_DEFINED
+
+#include "SkImageFilter.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:
+    explicit 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;
+};
+
+#endif