Revert of Implement SkImageFilter::Cache with SkResourceCache.

src/core/SkResourceCache.cpp

Index: src/core/SkResourceCache.cpp
diff --git a/src/core/SkResourceCache.cpp b/src/core/SkResourceCache.cpp
index a79c9539b985b8fcca54bd97ea1dea616d7de3ac..54091f1fd4462e3088c1d7e13031a3202792c04e 100644
--- a/src/core/SkResourceCache.cpp
+++ b/src/core/SkResourceCache.cpp
@@ -658,6 +658,7 @@
 }
 
 void SkGraphics::PurgeResourceCache() {
+    SkImageFilter::PurgeCache();
     return SkResourceCache::PurgeAll();
 }