Make XML compilation conditional.

tests/SkDOMTest.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "Test.h"
+
+#if defined(SK_XML)
+
 #include "SkDOM.h"
-#include "Test.h"
 
 DEF_TEST(SkDOM_test, r) {
     static const char gDoc[] =
         "<root a='1' b='2'>"
             "<elem1 c='3' />"
             "<elem2 d='4' />"
             "<elem3 e='5'>"
                 "<subelem1/>"
                 "<subelem2 f='6' g='7'/>"
             "</elem3>"
@@ skipping 10 matching lines @@
     const char* v = dom.findAttr(root, "a");
     REPORTER_ASSERT(r, v && !strcmp(v, "1"));
     v = dom.findAttr(root, "b");
     REPORTER_ASSERT(r, v && !strcmp(v, "2"));
     v = dom.findAttr(root, "c");
     REPORTER_ASSERT(r, v == nullptr);
 
     REPORTER_ASSERT(r, dom.getFirstChild(root, "elem1"));
     REPORTER_ASSERT(r, !dom.getFirstChild(root, "subelem1"));
 }
+
+#endif // SK_XML