Revert "Revert "replace SkXfermode obj with SkBlendMode enum in paints""

This reverts commit ce02e7175872abde3721df9e5d3ec0ab8384cd8e.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2878

Change-Id: I86875511a13497112827cbaed1dbd7639e9e3d10
Reviewed-on: https://skia-review.googlesource.com/2878
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/tools/debugger/SkDebugCanvas.cpp b/tools/debugger/SkDebugCanvas.cpp
index f15c68c..1da995b 100644
--- a/tools/debugger/SkDebugCanvas.cpp
+++ b/tools/debugger/SkDebugCanvas.cpp
@@ -42,7 +42,8 @@
         if (*paint) {
             if (nullptr != fOverdrawXfermode.get()) {
                 paint->writable()->setAntiAlias(false);
-                paint->writable()->setXfermode(fOverdrawXfermode);
+                // TODO: replace overdraw mode with something else
+//                paint->writable()->setXfermode(fOverdrawXfermode);
             }
 
             if (fOverrideFilterQuality) {