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 62fba1ac48659848f6a1314ca6ca2dd018928a74..15e93c11cdd336d0b76420e3222bcf8e8490b603 100644
--- a/src/effects/SkDisplacementMapEffect.cpp
+++ b/src/effects/SkDisplacementMapEffect.cpp
@@ -19,6 +19,8 @@
 
 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");
@@ -602,7 +604,7 @@ 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;
 }