Enable QUIC's pacing by default on all QUIC connections by setting

net/tools/quic/end_to_end_test.cc

Index: net/tools/quic/end_to_end_test.cc
diff --git a/net/tools/quic/end_to_end_test.cc b/net/tools/quic/end_to_end_test.cc
index c890f141c5752aa95b68341443e80f04fb32ef88..9e7605f6df19b6ed2ff0909caa6adc995eb33df9 100644
--- a/net/tools/quic/end_to_end_test.cc
+++ b/net/tools/quic/end_to_end_test.cc
@@ -319,6 +319,8 @@ class EndToEndTest : public ::testing::TestWithParam<TestParams> {
     // and TestWriterFactory when Initialize() is executed.
     client_writer_ = new PacketDroppingTestWriter();
     server_writer_ = new PacketDroppingTestWriter();
+    // TODO(ianswett): Remove this once it's fully rolled out.
+    FLAGS_quic_enable_pacing = false;
   }
 
   void TearDown() override { StopServer(); }