[SVG] Implement 'discard' element

LayoutTests/svg/animations/discard-on-discard-expected.txt

Index: LayoutTests/svg/animations/discard-on-discard-expected.txt
diff --git a/LayoutTests/svg/animations/discard-on-discard-expected.txt b/LayoutTests/svg/animations/discard-on-discard-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..da439b82db0c8dbfa82fdb0fb3fcd64624efd109
--- /dev/null
+++ b/LayoutTests/svg/animations/discard-on-discard-expected.txt
@@ -0,0 +1,30 @@
+SVG 1.1 dynamic animation tests
+
+
+Test the behavior of one discard applied on another discard
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS colorComponents[1] is 255
+PASS colorComponents[2] is 0
+PASS colorComponents[3] is 0
+PASS colorComponents[1] is 255
+PASS colorComponents[2] is 0
+PASS colorComponents[3] is 0
+PASS colorComponents[1] is 0
+PASS colorComponents[2] is 255
+PASS colorComponents[3] is 0
+PASS colorComponents[1] is 0
+PASS colorComponents[2] is 255
+PASS colorComponents[3] is 0
+PASS colorComponents[1] is 0
+PASS colorComponents[2] is 255
+PASS colorComponents[3] is 0
+PASS colorComponents[1] is 0
+PASS colorComponents[2] is 255
+PASS colorComponents[3] is 0
+PASS successfullyParsed is true
+
+TEST COMPLETE
+