rtc::Buffer: Accept void* in addition to the byte-sized types

We used to accept void* (until 9478437f), and we'll have to continue
to do so for a little while longer, until Chromium doesn't need it
anymore.

TBR=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48179004

Cr-Commit-Position: refs/heads/master@{#9035}
diff --git a/webrtc/base/buffer.h b/webrtc/base/buffer.h
index 5880f50..8959b40 100644
--- a/webrtc/base/buffer.h
+++ b/webrtc/base/buffer.h
@@ -40,6 +40,20 @@
   using t = decltype(F(static_cast<T*>(nullptr)));
 };
 
+// Deprecated: Accept void* in addition to the byte-sized types.
+// TODO(kwiberg): Remove once Chromium doesn't need this anymore.
+template <typename T>
+struct ByteTypeOrVoid {
+ private:
+  static int F(uint8_t*);
+  static int F(int8_t*);
+  static int F(char*);
+  static int F(void*);
+
+ public:
+  using t = decltype(F(static_cast<T*>(nullptr)));
+};
+
 }  // namespace internal
 
 // Basic buffer class, can be grown and shrunk dynamically.
@@ -56,10 +70,10 @@
 
   // Construct a buffer and copy the specified number of bytes into it. The
   // source array may be (const) uint8_t*, int8_t*, or char*.
-  template <typename T, typename internal::ByteType<T>::t = 0>
+  template <typename T, typename internal::ByteTypeOrVoid<T>::t = 0>
   Buffer(const T* data, size_t size)
       : Buffer(data, size, size) {}
-  template <typename T, typename internal::ByteType<T>::t = 0>
+  template <typename T, typename internal::ByteTypeOrVoid<T>::t = 0>
   Buffer(const T* data, size_t size, size_t capacity)
       : Buffer(size, capacity) {
     std::memcpy(data_.get(), data, size);
@@ -119,7 +133,7 @@
 
   // Replace the contents of the buffer. Accepts the same types as the
   // constructors.
-  template <typename T, typename internal::ByteType<T>::t = 0>
+  template <typename T, typename internal::ByteTypeOrVoid<T>::t = 0>
   void SetData(const T* data, size_t size) {
     assert(IsConsistent());
     size_ = 0;
@@ -132,7 +146,7 @@
   void SetData(const Buffer& buf) { SetData(buf.data(), buf.size()); }
 
   // Append data to the buffer. Accepts the same types as the constructors.
-  template <typename T, typename internal::ByteType<T>::t = 0>
+  template <typename T, typename internal::ByteTypeOrVoid<T>::t = 0>
   void AppendData(const T* data, size_t size) {
     assert(IsConsistent());
     const size_t new_size = size_ + size;