Revert "replace SkXfermode obj with SkBlendMode enum in paints"

This reverts commit I4fb489ba6b3f77b458f7e4a99f79c7ad10859135.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> replace SkXfermode obj with SkBlendMode enum in paints
> 
> BUG=skia:5814
> 
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2714
> 
> Change-Id: I4fb489ba6b3f77b458f7e4a99f79c7ad10859135
> Reviewed-on: https://skia-review.googlesource.com/2714
> Reviewed-by: Florin Malita <fmalita@chromium.org>
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Mike Reed <reed@google.com>
> 

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

Change-Id: I3e43f79ef5c1709929663fe63cc1f67cd78270b7
Reviewed-on: https://skia-review.googlesource.com/2871
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/xfermodes3.cpp b/gm/xfermodes3.cpp
index 36702bf..300b78f 100644
--- a/gm/xfermodes3.cpp
+++ b/gm/xfermodes3.cpp
@@ -69,7 +69,7 @@
         };
         for (size_t s = 0; s < SK_ARRAY_COUNT(kStrokes); ++s) {
             for (size_t m = 0; m <= SkXfermode::kLastMode; ++m) {
-                SkBlendMode mode = static_cast<SkBlendMode>(m);
+                SkXfermode::Mode mode = static_cast<SkXfermode::Mode>(m);
                 canvas->drawText(SkXfermode::ModeName(mode),
                                  strlen(SkXfermode::ModeName(mode)),
                                  SkIntToScalar(x),
@@ -77,7 +77,7 @@
                                  labelP);
                 for (size_t c = 0; c < SK_ARRAY_COUNT(kSolidColors); ++c) {
                     SkPaint modePaint;
-                    modePaint.setBlendMode(mode);
+                    modePaint.setXfermodeMode(mode);
                     modePaint.setColor(kSolidColors[c]);
                     modePaint.setStyle(kStrokes[s].fStyle);
                     modePaint.setStrokeWidth(kStrokes[s].fWidth);
@@ -93,7 +93,7 @@
                 }
                 for (size_t a = 0; a < SK_ARRAY_COUNT(kBmpAlphas); ++a) {
                     SkPaint modePaint;
-                    modePaint.setBlendMode(mode);
+                    modePaint.setXfermodeMode(mode);
                     modePaint.setAlpha(kBmpAlphas[a]);
                     modePaint.setShader(fBmpShader);
                     modePaint.setStyle(kStrokes[s].fStyle);