Improve XML serialization, URI parsing, and XPath node set processing.

third_party/libxml/chromium/libxml2-2.9.4-xmlDumpElementContent-null-deref.patch

Index: third_party/libxml/chromium/libxml2-2.9.4-xmlDumpElementContent-null-deref.patch
diff --git a/third_party/libxml/chromium/libxml2-2.9.4-xmlDumpElementContent-null-deref.patch b/third_party/libxml/chromium/libxml2-2.9.4-xmlDumpElementContent-null-deref.patch
new file mode 100644
index 0000000000000000000000000000000000000000..ec28c85202aae879a9db48d5d46b2f25a69182c3
--- /dev/null
+++ b/third_party/libxml/chromium/libxml2-2.9.4-xmlDumpElementContent-null-deref.patch
@@ -0,0 +1,34 @@
+observed while fuzzing
+
+--- src/valid.c
++++ src/valid.c
+@@ -1172,12 +1172,14 @@ xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob)
+ 	    xmlBufferWriteCHAR(buf, content->name);
+ 	    break;
+ 	case XML_ELEMENT_CONTENT_SEQ:
++	    if (content->c1 == NULL) return;
+ 	    if ((content->c1->type == XML_ELEMENT_CONTENT_OR) ||
+ 	        (content->c1->type == XML_ELEMENT_CONTENT_SEQ))
+ 		xmlDumpElementContent(buf, content->c1, 1);
+ 	    else
+ 		xmlDumpElementContent(buf, content->c1, 0);
+             xmlBufferWriteChar(buf, " , ");
++	    if (content->c2 == NULL) return;
+ 	    if ((content->c2->type == XML_ELEMENT_CONTENT_OR) ||
+ 	        ((content->c2->type == XML_ELEMENT_CONTENT_SEQ) &&
+ 		 (content->c2->ocur != XML_ELEMENT_CONTENT_ONCE)))
+@@ -1186,12 +1188,14 @@ xmlDumpElementContent(xmlBufferPtr buf, xmlElementContentPtr content, int glob)
+ 		xmlDumpElementContent(buf, content->c2, 0);
+ 	    break;
+ 	case XML_ELEMENT_CONTENT_OR:
++	    if (content->c1 == NULL) return;
+ 	    if ((content->c1->type == XML_ELEMENT_CONTENT_OR) ||
+ 	        (content->c1->type == XML_ELEMENT_CONTENT_SEQ))
+ 		xmlDumpElementContent(buf, content->c1, 1);
+ 	    else
+ 		xmlDumpElementContent(buf, content->c1, 0);
+             xmlBufferWriteChar(buf, " | ");
++	    if (content->c2 == NULL) return;
+ 	    if ((content->c2->type == XML_ELEMENT_CONTENT_SEQ) ||
+ 	        ((content->c2->type == XML_ELEMENT_CONTENT_OR) &&
+ 		 (content->c2->ocur != XML_ELEMENT_CONTENT_ONCE)))