Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/base/copyonwritebuffer_unittest.cc

Index: webrtc/base/copyonwritebuffer_unittest.cc
diff --git a/webrtc/base/copyonwritebuffer_unittest.cc b/webrtc/base/copyonwritebuffer_unittest.cc
index a95ad67a03e6ec2c41ad1210d3ae241f590ed3e7..21ac73198f5843bd85b78d864c6e590d944058e8 100644
--- a/webrtc/base/copyonwritebuffer_unittest.cc
+++ b/webrtc/base/copyonwritebuffer_unittest.cc
@@ -41,6 +41,13 @@ void EnsureBuffersDontShareData(const CopyOnWriteBuffer& buf1,
   EXPECT_NE(data1, data2);
 }
 
+TEST(CopyOnWriteBufferTest, TestCreateEmptyData) {
+  CopyOnWriteBuffer buf(static_cast<const uint8_t*>(nullptr), 0);
+  EXPECT_EQ(buf.size(), 0u);
+  EXPECT_EQ(buf.capacity(), 0u);
+  EXPECT_EQ(buf.data(), nullptr);
+}
+
 TEST(CopyOnWriteBufferTest, TestMoveConstruct) {
   CopyOnWriteBuffer buf1(kTestData, 3, 10);
   size_t buf1_size = buf1.size();
@@ -125,6 +132,21 @@ TEST(CopyOnWriteBufferTest, TestSetData) {
   EnsureBuffersDontShareData(buf1, buf3);
   const int8_t exp[] = {'f', 'o', 'o', 0x0};
   EXPECT_EQ(buf3, CopyOnWriteBuffer(exp));
+
+  buf2.SetData(static_cast<const uint8_t*>(nullptr), 0u);
+  EnsureBuffersDontShareData(buf1, buf2);
+  EXPECT_EQ(buf1.size(), 3u);
+  EXPECT_EQ(buf1.capacity(), 10u);
+  EXPECT_EQ(buf2.size(), 0u);
+  EXPECT_EQ(buf2.capacity(), 0u);
+}
+
+TEST(CopyOnWriteBufferTest, TestSetDataEmpty) {
+  CopyOnWriteBuffer buf;
+  buf.SetData(static_cast<const uint8_t*>(nullptr), 0u);
+  EXPECT_EQ(buf.size(), 0u);
+  EXPECT_EQ(buf.capacity(), 0u);
+  EXPECT_EQ(buf.data(), nullptr);
 }
 
 TEST(CopyOnWriteBufferTest, TestEnsureCapacity) {