Adding comments to the existing SVG reftests indicating where they came from to make it easier to figure things out when regressions occur

layout/reftests/svg/foreignObject-display-01.svg

@@ -1,11 +1,14 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      onload="setTimeout(handleLoad, 0);">
+
   <title>Testcase for removing display:none from foreignObject child</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=281260 -->
+
   <script type="application/ecmascript">
   <![CDATA[
 
-// This is from https://bugzilla.mozilla.org/show_bug.cgi?id=281260
-// The setTimeout is necessary since it was _after_ loading that we failed
+// This must be called using setTimeout since it was _after_ loading we failed
 
 function handleLoad(event)
 {

layout/reftests/svg/getElementById-a-element-01.svg

@@ -1,6 +1,10 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      onload="handleLoad(evt);">
+
   <title>Testcase for getElementById finding &lt;a&gt; element</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=320724 -->
+
   <script type="application/ecmascript">
   <![CDATA[
 

layout/reftests/svg/pseudo-classes-01.svg

@@ -1,6 +1,10 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      xmlns:xlink="http://www.w3.org/1999/xlink">
+
   <title>Testcase for the :first-child, :link, :visited and :lang pseudo-classes</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=268135 -->
+
   <style type="text/css">
   <![CDATA[
 

layout/reftests/svg/pseudo-classes-02-ref.svg

@@ -1,5 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      xmlns:xlink="http://www.w3.org/1999/xlink">
+
   <title>Reference for pseudo-classes and text/links</title>
 
   <!-- link in text -->

layout/reftests/svg/pseudo-classes-02.svg

@@ -1,6 +1,10 @@
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1"
      xmlns:xlink="http://www.w3.org/1999/xlink">
+
   <title>Testcase for pseudo-classes and text/links</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=268135 -->
+
   <style type="text/css">
   <![CDATA[