[svg] Allow clients to pass a custom SkFontMgr

Introduce a Builder helper and plumb the client-provided SkFontMgr for
font resolution.

Also clean up some of the legacy SkSVGDom factories.

Bug: skia:10840
Change-Id: I6e1eabe7c257cb75dfdb5bf67054f93f25769027
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/333577
Commit-Queue: Florin Malita <fmalita@google.com>
Reviewed-by: Tyler Denniston <tdenniston@google.com>
diff --git a/modules/svg/utils/SvgTool.cpp b/modules/svg/utils/SvgTool.cpp
index e78e686..71ab3c3 100644
--- a/modules/svg/utils/SvgTool.cpp
+++ b/modules/svg/utils/SvgTool.cpp
@@ -39,7 +39,10 @@
         return 1;
     }
 
-    auto svg_dom = SkSVGDOM::MakeFromStream(in);
+
+    auto svg_dom = SkSVGDOM::Builder()
+                        .setFontManager(SkFontMgr::RefDefault())
+                        .make(in);
     if (!svg_dom) {
         std::cerr << "Could not parse " << FLAGS_input[0] << "\n";
         return 1;