Register some flattenable factories.

Now, SkComposeShaders, SkDiscreteMapper, SkCosineMapper,
Line2DPathEffect, and SkTransparentShader can be flattened
and unflattened. This makes more of our samples work when
using a pipe.

Review URL: https://codereview.appspot.com/6338064

git-svn-id: http://skia.googlecode.com/svn/trunk@4334 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleAll.cpp b/samplecode/SampleAll.cpp
index 201dfe7..303059b 100644
--- a/samplecode/SampleAll.cpp
+++ b/samplecode/SampleAll.cpp
@@ -250,6 +250,8 @@
     typedef Sk2DPathEffect INHERITED;
 };
 
+SK_DEFINE_FLATTENABLE_REGISTRAR(Line2DPathEffect)
+
 static void r9(SkLayerRasterizer* rast, SkPaint& p) {
     rast->addLayer(p);