Make request fail with ERR_CONTENT_DECODING_INIT_FAILED if sdch is not supported

net/filter/sdch_policy_delegate.cc

Index: net/filter/sdch_policy_delegate.cc
diff --git a/net/filter/sdch_policy_delegate.cc b/net/filter/sdch_policy_delegate.cc
index 82b6541b285b15da693180d302212f861a1be4ce..e652445e509b8b718c96693f55938f70c437a35e 100644
--- a/net/filter/sdch_policy_delegate.cc
+++ b/net/filter/sdch_policy_delegate.cc
@@ -133,7 +133,9 @@ SdchPolicyDelegate::SdchPolicyDelegate(
       sdch_manager_(sdch_manager),
       dictionary_set_(std::move(dictionary_set)),
       response_code_(response_code),
-      net_log_(net_log) {}
+      net_log_(net_log) {
+  DCHECK(sdch_manager_);
+}
 
 SdchPolicyDelegate::~SdchPolicyDelegate() {}