add virtuals to optimize composing colorfilters

src/core/SkColorFilter.cpp

Index: src/core/SkColorFilter.cpp
diff --git a/src/core/SkColorFilter.cpp b/src/core/SkColorFilter.cpp
index d49fc52fa1b68aea0a15b116dc08bb3c1c80daf8..2a78058106a01b2266190b0a7ccbc5b21fa6b377 100644
--- a/src/core/SkColorFilter.cpp
+++ b/src/core/SkColorFilter.cpp
@@ -104,6 +104,8 @@ SkFlattenable* SkComposeColorFilter::CreateProc(SkReadBuffer& buffer) {
     return CreateComposeFilter(outer, inner);
 }
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
 SkColorFilter* SkColorFilter::CreateComposeFilter(SkColorFilter* outer, SkColorFilter* inner) {
     if (!outer) {
         return SkSafeRef(inner);
@@ -111,7 +113,13 @@ SkColorFilter* SkColorFilter::CreateComposeFilter(SkColorFilter* outer, SkColorF
     if (!inner) {
         return SkSafeRef(outer);
     }
-    return SkNEW_ARGS(SkComposeColorFilter, (outer, inner));
+
+    // Give the subclass a shot at a more optimal composition...
+    SkColorFilter* composition = outer->newComposed(inner);
+    if (NULL == composition) {
+        composition = SkNEW_ARGS(SkComposeColorFilter, (outer, inner));
+    }
+    return composition;
 }
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkColorFilter)