Convert all webrtc code to not access EncodedImage::_size directly.

Read using capacity() method, write using set_buffer() method. This is
a preparation for making the member private, and renaming it to
capacity_.

Bug: webrtc:9378
Change-Id: I2f96679d052a83fe81be40301bd9863c87074640
Reviewed-on: https://webrtc-review.googlesource.com/c/113520
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25934}
diff --git a/modules/video_coding/encoded_frame.cc b/modules/video_coding/encoded_frame.cc
index b46f759..ad28ec2 100644
--- a/modules/video_coding/encoded_frame.cc
+++ b/modules/video_coding/encoded_frame.cc
@@ -152,16 +152,17 @@
 }
 
 void VCMEncodedFrame::VerifyAndAllocate(size_t minimumSize) {
-  if (minimumSize > _size) {
+  size_t old_capacity = capacity();
+  if (minimumSize > old_capacity) {
     // create buffer of sufficient size
-    uint8_t* newBuffer = new uint8_t[minimumSize];
-    if (_buffer) {
+    uint8_t* old_buffer = _buffer;
+
+    set_buffer(new uint8_t[minimumSize], minimumSize);
+    if (old_buffer) {
       // copy old data
-      memcpy(newBuffer, _buffer, _size);
-      delete[] _buffer;
+      memcpy(_buffer, old_buffer, old_capacity);
+      delete[] old_buffer;
     }
-    _buffer = newBuffer;
-    _size = minimumSize;
   }
 }