Add fuzz testers to //net for some functions with simple parsing APIs.

net/base/data_url.cc

Index: net/base/data_url.cc
diff --git a/net/base/data_url.cc b/net/base/data_url.cc
index 07b8fb00bb5344dcc02dd1bb20950aabcd344fe0..4d29bf6f128f8d5ef078c6369c19b6755cb0cfa6 100644
--- a/net/base/data_url.cc
+++ b/net/base/data_url.cc
@@ -21,6 +21,9 @@ namespace net {
 // static
 bool DataURL::Parse(const GURL& url, std::string* mime_type,
                     std::string* charset, std::string* data) {
+  if (!url.is_valid())
+    return false;
+
   DCHECK(mime_type->empty());
   DCHECK(charset->empty());
   std::string::const_iterator begin = url.spec().begin();