Factory methods for heap-allocated SkImageFilter objects.

src/effects/SkDisplacementMapEffect.cpp

Index: src/effects/SkDisplacementMapEffect.cpp
diff --git a/src/effects/SkDisplacementMapEffect.cpp b/src/effects/SkDisplacementMapEffect.cpp
index cffadb2e660ddca7111a4c0c2dbcd3a825949688..b221c4b29e08382a1bdb99b4293f9e506efa7f10 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -20,6 +20,8 @@
 
 namespace {
 
+#define kChannelSelectorKeyBits 3; // Max value is 4, so 3 bits are required at most
+
 template<SkDisplacementMapEffect::ChannelSelectorType type>
 uint32_t getValue(SkColor, const SkUnPreMultiply::Scale*) {
     SkDEBUGFAIL("Unknown channel selector");
@@ -601,7 +603,7 @@ GrGLEffect::EffectKey GrGLDisplacementMapEffect::GenKey(const GrDrawEffect& draw
         drawEffect.castEffect<GrDisplacementMapEffect>();
 
     EffectKey xKey = displacementMap.xChannelSelector();
-    EffectKey yKey = displacementMap.yChannelSelector() << SkDisplacementMapEffect::kKeyBits;
+    EffectKey yKey = displacementMap.yChannelSelector() << kChannelSelectorKeyBits;
 
     return xKey | yKey;
 }