Revert[5] "replace SkXfermode obj with SkBlendMode enum in paints"

This reverts commit I0fa5c58af428f3da8565465d1219a34ef8417d9a.

Reason for revert: failing to deserialize some of the 100K

Original change's description:
> Revert[4] "replace SkXfermode obj with SkBlendMode enum in paints"
> 
> This reverts commit 2cbcd12281ee807214df094964c584c78932e10b.
> 
> BUG=skia:
> 
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2924
> 
> Change-Id: I0fa5c58af428f3da8565465d1219a34ef8417d9a
> Reviewed-on: https://skia-review.googlesource.com/2924
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Mike Reed <reed@google.com>
> 

TBR=reed@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I1805a57eef5ebcac203da5989c8539345ecf806f
Reviewed-on: https://skia-review.googlesource.com/2962
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/samplecode/SampleLayers.cpp b/samplecode/SampleLayers.cpp
index 71b2e8b..52e6593 100644
--- a/samplecode/SampleLayers.cpp
+++ b/samplecode/SampleLayers.cpp
@@ -31,7 +31,7 @@
     SkPoint pts[] = { { 0, 0 }, { 0, SK_Scalar1*20 } };
     paint->setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, 2,
                                                   SkShader::kClamp_TileMode, 0, &localMatrix));
-    paint->setBlendMode(SkBlendMode::kDstIn);
+    paint->setXfermodeMode(SkXfermode::kDstIn_Mode);
 }
 
 // test drawing with strips of fading gradient above and below
@@ -141,7 +141,7 @@
             canvas->saveLayer(&r, &p);
             canvas->drawColor(0xFFFF0000);
             p.setAlpha(0);  // or 0
-            p.setBlendMode(SkBlendMode::kSrc);
+            p.setXfermodeMode(SkXfermode::kSrc_Mode);
             canvas->drawOval(r, p);
             canvas->restore();
             return;