[svg] Add feFlood filter node

Several related W3C tests still won't pass until we implement the filter
primitive subregion.

Bug: skia:10841
Change-Id: I9e4beb9da8aa769f23a979ad5116a38fcda85ca4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/343105
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Tyler Denniston <tdenniston@google.com>
diff --git a/modules/svg/src/SkSVGAttribute.cpp b/modules/svg/src/SkSVGAttribute.cpp
index d07aa91..843437c 100644
--- a/modules/svg/src/SkSVGAttribute.cpp
+++ b/modules/svg/src/SkSVGAttribute.cpp
@@ -36,6 +36,8 @@
 
     result.fStopColor.set(SkSVGColor(SK_ColorBLACK));
     result.fStopOpacity.set(SkSVGNumberType(1));
+    result.fFloodColor.set(SkSVGColor(SK_ColorBLACK));
+    result.fFloodOpacity.set(SkSVGNumberType(1));
 
     return result;
 }