Add QuicStrCat.

net/quic/core/quic_headers_stream.cc

Index: net/quic/core/quic_headers_stream.cc
diff --git a/net/quic/core/quic_headers_stream.cc b/net/quic/core/quic_headers_stream.cc
index 0ea432abf27b8788cffc14c761daac3088c3f4dd..ce8d5e287c2fdd5bc47d15d23389f917492b7c53 100644
--- a/net/quic/core/quic_headers_stream.cc
+++ b/net/quic/core/quic_headers_stream.cc
@@ -149,9 +149,9 @@ class QuicHeadersStream::SpdyFramerVisitor
   }
 
   void OnError(SpdyFramer* framer) override {
-    CloseConnection(base::StringPrintf(
-        "SPDY framing error: %s",
-        SpdyFramer::ErrorCodeToString(framer->error_code())));
+    CloseConnection(
+        QuicStrCat("SPDY framing error: ",
+                   SpdyFramer::ErrorCodeToString(framer->error_code())));
   }
 
   void OnDataFrameHeader(SpdyStreamId stream_id,
@@ -182,15 +182,15 @@ class QuicHeadersStream::SpdyFramerVisitor
             stream_->session()->perspective() == Perspective::IS_SERVER) {
           // See rfc7540, Section 6.5.2.
           if (value > 1) {
-            CloseConnection("Invalid value for SETTINGS_ENABLE_PUSH: " +
-                            base::IntToString(value));
+            CloseConnection(
+                QuicStrCat("Invalid value for SETTINGS_ENABLE_PUSH: ", value));
             return;
           }
           stream_->UpdateEnableServerPush(value > 0);
           break;
         } else {
-          CloseConnection("Unsupported field of HTTP/2 SETTINGS frame: " +
-                          base::IntToString(id));
+          CloseConnection(
+              QuicStrCat("Unsupported field of HTTP/2 SETTINGS frame: ", id));
         }
         break;
       // TODO(fayang): Need to support SETTINGS_MAX_HEADER_LIST_SIZE when
@@ -200,8 +200,8 @@ class QuicHeadersStream::SpdyFramerVisitor
           break;
         }
       default:
-        CloseConnection("Unsupported field of HTTP/2 SETTINGS frame: " +
-                        base::IntToString(id));
+        CloseConnection(
+            QuicStrCat("Unsupported field of HTTP/2 SETTINGS frame: ", id));
     }
   }