rtc::Buffer: Rename length to size, for conformance with the STL

And add a constructor for creating an uninitialized Buffer of a
specified size.

(I intend to follow up with more Buffer changes, but since it's rather
widely used, the rename is quite noisy and works better as a separate
CL.)

R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48579004

Cr-Commit-Position: refs/heads/master@{#8841}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8841 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/buffer.h b/webrtc/base/buffer.h
index a7bc570..c7fb959 100644
--- a/webrtc/base/buffer.h
+++ b/webrtc/base/buffer.h
@@ -23,50 +23,49 @@
 class Buffer {
  public:
   Buffer();
-  Buffer(const void* data, size_t length);
-  Buffer(const void* data, size_t length, size_t capacity);
+  explicit Buffer(size_t size);
+  Buffer(const void* data, size_t size);
+  Buffer(const void* data, size_t size, size_t capacity);
   Buffer(const Buffer& buf);
   ~Buffer();
 
   const char* data() const { return data_.get(); }
   char* data() { return data_.get(); }
-  // TODO: should this be size(), like STL?
-  size_t length() const { return length_; }
+  size_t size() const { return size_; }
   size_t capacity() const { return capacity_; }
 
   Buffer& operator=(const Buffer& buf) {
     if (&buf != this) {
-      Construct(buf.data(), buf.length(), buf.length());
+      Construct(buf.data(), buf.size(), buf.size());
     }
     return *this;
   }
   bool operator==(const Buffer& buf) const {
-    return (length_ == buf.length() &&
-            memcmp(data_.get(), buf.data(), length_) == 0);
+    return (size_ == buf.size() && memcmp(data_.get(), buf.data(), size_) == 0);
   }
   bool operator!=(const Buffer& buf) const {
     return !operator==(buf);
   }
 
-  void SetData(const void* data, size_t length) {
-    ASSERT(data != NULL || length == 0);
-    SetLength(length);
-    memcpy(data_.get(), data, length);
+  void SetData(const void* data, size_t size) {
+    ASSERT(data != NULL || size == 0);
+    SetSize(size);
+    memcpy(data_.get(), data, size);
   }
-  void AppendData(const void* data, size_t length) {
-    ASSERT(data != NULL || length == 0);
-    size_t old_length = length_;
-    SetLength(length_ + length);
-    memcpy(data_.get() + old_length, data, length);
+  void AppendData(const void* data, size_t size) {
+    ASSERT(data != NULL || size == 0);
+    size_t old_size = size_;
+    SetSize(size_ + size);
+    memcpy(data_.get() + old_size, data, size);
   }
-  void SetLength(size_t length) {
-    SetCapacity(length);
-    length_ = length;
+  void SetSize(size_t size) {
+    SetCapacity(size);
+    size_ = size;
   }
   void SetCapacity(size_t capacity) {
     if (capacity > capacity_) {
       rtc::scoped_ptr<char[]> data(new char[capacity]);
-      memcpy(data.get(), data_.get(), length_);
+      memcpy(data.get(), data_.get(), size_);
       data_.swap(data);
       capacity_ = capacity;
     }
@@ -75,19 +74,19 @@
   void TransferTo(Buffer* buf) {
     ASSERT(buf != NULL);
     buf->data_.reset(data_.release());
-    buf->length_ = length_;
+    buf->size_ = size_;
     buf->capacity_ = capacity_;
     Construct(NULL, 0, 0);
   }
 
  protected:
-  void Construct(const void* data, size_t length, size_t capacity) {
+  void Construct(const void* data, size_t size, size_t capacity) {
     data_.reset(new char[capacity_ = capacity]);
-    SetData(data, length);
+    SetData(data, size);
   }
 
   scoped_ptr<char[]> data_;
-  size_t length_;
+  size_t size_;
   size_t capacity_;
 };