Move header-ordering validation from hpack decoder to header validator.

net/spdy/header_coalescer.cc

Index: net/spdy/header_coalescer.cc
diff --git a/net/spdy/header_coalescer.cc b/net/spdy/header_coalescer.cc
index 03357c90dfdc43af9f7aa83c8062f76231c09cc0..71624179d5d293f3ae4b01d5d05f0c2819bae2f9 100644
--- a/net/spdy/header_coalescer.cc
+++ b/net/spdy/header_coalescer.cc
@@ -15,6 +15,15 @@ void HeaderCoalescer::OnHeader(base::StringPiece key, base::StringPiece value) {
     return;
   }
 
+  if (key[0] == ':') {
+    if (regular_header_seen_) {
+      error_seen_ = true;
+      return;
+    }
+  } else {
+    regular_header_seen_ = true;
+  }
+
   auto iter = headers_.find(key);
   if (iter == headers_.end()) {
     headers_[key] = value;