Revert of modify nothingToDraw to notice filters

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 4ccfce235acc228c1690545bbba9f56bbf186334..ebdc866d653b5b787862ae3d5ebd86524cb09b4e 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -2377,18 +2377,6 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
-// return true if the filter exists, and may affect alpha
-static bool affects_alpha(const SkColorFilter* cf) {
-    return cf && !(cf->getFlags() & SkColorFilter::kAlphaUnchanged_Flag);
-}
-
-// return true if the filter exists, and may affect alpha
-static bool affects_alpha(const SkImageFilter* imf) {
-    // TODO: check if we should allow imagefilters to broadcast that they don't affect alpha
-    // ala colorfilters
-    return imf != NULL;
-}
-
 bool SkPaint::nothingToDraw() const {
     if (fLooper) {
         return false;
@@ -2401,10 +2389,7 @@
             case SkXfermode::kDstOut_Mode:
             case SkXfermode::kDstOver_Mode:
             case SkXfermode::kPlus_Mode:
-                if (0 == this->getAlpha()) {
-                    return !affects_alpha(fColorFilter) && !affects_alpha(fImageFilter);
-                }
-                break;
+                return 0 == this->getAlpha();
             case SkXfermode::kDst_Mode:
                 return true;
             default: