Changed the semantics of Buffer::Clear to not alter the capacity

webrtc/base/buffer_unittest.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 159 matching lines @@
   using std::swap;
   swap(buf1, buf2);
   EXPECT_EQ(buf1.size(), 6u);
   EXPECT_EQ(buf1.capacity(), 40u);
   EXPECT_EQ(buf1.data(), data2);
   EXPECT_EQ(buf2.size(), 3u);
   EXPECT_EQ(buf2.capacity(), 3u);
   EXPECT_EQ(buf2.data(), data1);
 }
 
+TEST(BufferTest, TestClear) {
+  Buffer buf;
+  buf.SetData(kTestData, 15);
+  EXPECT_EQ(buf.size(), 15u);
+  EXPECT_EQ(buf.capacity(), 15u);
+  const char *data = buf.data<char>();
+  buf.Clear();
+  EXPECT_EQ(buf.size(), 0u);
+  EXPECT_EQ(buf.capacity(), 15u);  // Hasn't shrunk.
+  EXPECT_EQ(buf.data<char>(), data); // No reallocation.
+}
+
 }  // namespace rtc