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

webrtc/base/buffer_unittest.cc

Index: webrtc/base/buffer_unittest.cc
diff --git a/webrtc/base/buffer_unittest.cc b/webrtc/base/buffer_unittest.cc
index 0b93b9b56e8d54afdd4b5d89964023f75c0cbb5f..f917bc6181e3a1394e0c08208d6febb50441ffca 100644
--- a/webrtc/base/buffer_unittest.cc
+++ b/webrtc/base/buffer_unittest.cc
@@ -177,4 +177,16 @@ TEST(BufferTest, TestSwap) {
   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