add SK_SUPPORT_LEGACY_IMAGEFILTER_CTM to guard skia change

see https://codereview.chromium.org/1140943004/

BUG=
NOTRY=True
just adds a new flag for future cls

Review URL: https://codereview.chromium.org/1133403003

Cr-Commit-Position: refs/heads/master@{#329841}

skia/config/SkUserConfig.h

@@ -245,6 +245,10 @@ SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
 #   define SK_SUPPORT_LEGACY_GETTOPDEVICE
 #endif
 
+#ifndef    SK_SUPPORT_LEGACY_IMAGEFILTER_CTM
+#   define SK_SUPPORT_LEGACY_IMAGEFILTER_CTM
+#endif
+
 #ifndef    SK_LEGACY_DRAWPICTURECALLBACK
 #   define SK_LEGACY_DRAWPICTURECALLBACK
 #endif