Remove an unused local variable in quic_in_memory_cache.cc, only used

for testing.

Merge internal CL: 71210916

R=rtenneti@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/393143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283464 0039d316-1c4b-4281-b951-d872f2087c98

net/tools/quic/quic_in_memory_cache.cc

@@ -170,8 +170,6 @@ void QuicInMemoryCache::Initialize() {
                                        file_contents.length() - processed);
     }
 
-    string response_headers_str;
-    response_headers.DumpToString(&response_headers_str);
     if (!caching_visitor.done_framing()) {
       LOG(DFATAL) << "Did not frame entire message from file: " << file.value()
                   << " (" << processed << " of " << file_contents.length()