Cleanup: Pass std::string as const reference from media/

media/cast/test/end2end_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // This test generate synthetic data. For audio it's a sinusoid waveform with
 // frequency kSoundFrequency and different amplitudes. For video it's a pattern
 // that is shifting by one pixel per frame, each pixels neighbors right and down
 // is this pixels value +1, since the pixel value is 8 bit it will wrap
 // frequently within the image. Visually this will create diagonally color bands
 // that moves across the screen
@@ skipping 64 matching lines @@
 static const int kAudioFrameDurationMs = 10;
 
 // The amount of time between frame capture on the sender and playout on the
 // receiver.
 static const int kTargetPlayoutDelayMs = 100;
 
 // The maximum amount of deviation expected in the playout times emitted by the
 // receiver.
 static const int kMaxAllowedPlayoutErrorMs = 30;
 
-std::string ConvertFromBase16String(const std::string base_16) {
+std::string ConvertFromBase16String(const std::string& base_16) {
   std::string compressed;
   DCHECK_EQ(base_16.size() % 2, 0u) << "Must be a multiple of 2";
   compressed.reserve(base_16.size() / 2);
 
   std::vector<uint8> v;
   if (!base::HexStringToBytes(base_16, &v)) {
     NOTREACHED();
   }
   compressed.assign(reinterpret_cast<const char*>(&v[0]), v.size());
   return compressed;
@@ skipping 1416 matching lines @@
   EXPECT_LT(jump, 220u);
 }
 
 // TODO(pwestin): Add repeatable packet loss test.
 // TODO(pwestin): Add test for misaligned send get calls.
 // TODO(pwestin): Add more tests that does not resample.
 // TODO(pwestin): Add test when we have starvation for our RunTask.
 
 }  // namespace cast
 }  // namespace media