Fix !defined(SK_XML) builds

Add guards for dependent code.

TBR=
Change-Id: I49c0c90a2defc6f39589721f95562e9e0f17db13
Reviewed-on: https://skia-review.googlesource.com/144610
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/tools/viewer/SvgSlide.cpp b/tools/viewer/SvgSlide.cpp
index 41dc318..9ea9e40 100644
--- a/tools/viewer/SvgSlide.cpp
+++ b/tools/viewer/SvgSlide.cpp
@@ -7,6 +7,8 @@
 
 #include "SvgSlide.h"
 
+#if defined(SK_XML)
+
 #include "SkCanvas.h"
 #include "SkStream.h"
 #include "SkSVGDOM.h"
@@ -41,3 +43,5 @@
         fDom->render(canvas);
     }
 }
+
+#endif // SK_XML