Update handling of negative std.dev for feGaussianblur/feDropShadow

LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg

Index: LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg
diff --git a/LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg b/LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg
index 5304af05754c247721abcaf3522bb1b8f0d028df..7cd5d79b3136e4a33fed37705157982696b4e860 100644
--- a/LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg
+++ b/LayoutTests/svg/filters/feGaussianBlur-negative-deviation-expected.svg
@@ -1,6 +1,21 @@
 <?xml version="1.0" standalone="no"?>
-<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
-"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
-
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1">
+  <defs>
+    <filter id="f1">
+      <feGaussianBlur stdDeviation="0"/>
+    </filter>
+    <filter id="f2">
+      <feGaussianBlur stdDeviation="0 0"/>
+    </filter>
+    <filter id="f3">
+      <feGaussianBlur stdDeviation="1 0"/>
+    </filter>
+    <filter id="f4">
+      <feGaussianBlur stdDeviation="0 1"/>
+    </filter>
+  </defs>
+  <rect x="50" y="20" width="10" height="10" fill="green" filter="url(#f1)"/>
+  <rect x="50" y="40" width="10" height="10" fill="green" filter="url(#f2)"/>
+  <rect x="50" y="60" width="10" height="10" fill="green" filter="url(#f3)"/>
+  <rect x="50" y="80" width="10" height="10" fill="green" filter="url(#f4)"/>
 </svg>