VideoCapture: Remove deep frame copy in the border to libJingle

media/base/video_frame.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_VIDEO_FRAME_H_
 #define MEDIA_BASE_VIDEO_FRAME_H_
 
 #include <vector>
 
 #include "base/callback.h"
@@ skipping 247 matching lines @@
 
   // Returns the number of bytes per row and number of rows for a given plane.
   //
   // As opposed to stride(), row_bytes() refers to the bytes representing
   // frame data scanlines (coded_size.width() pixels, without stride padding).
   int row_bytes(size_t plane) const;
   int rows(size_t plane) const;
 
   // Returns pointer to the buffer for a given plane. The memory is owned by
   // VideoFrame object and must not be freed by the caller.
-  uint8* data(size_t plane) const;
+  const uint8* data(size_t plane) const;
+  uint8* data(size_t plane);

[scherkus (not reviewing), 2014/10/20 19:30:36]

do we need both the const and non-const versions?

could we get away with just having the uint8* version, or does that break
things?

AFAICT webrtc_video_capturer_adapter.cc should still compile upgrading a uint8*
-> const uint8*

[magjed_chromium, 2014/10/22 15:16:39]

Everything will compile and work using the old declaration:
uint8* data(size_t plane) const
but returning a non-const pointer to internal data from a const method goes
against the style guide. So that's the reason for having two methods: const
method returning const, and non-const method returning non-const.
Reference: 
http://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Use_of_const
"Declare methods to be const whenever possible. Accessors should almost always
be const. Other methods should be const if they do not modify any data members,
do not call any non-const methods, and do not return a non-const pointer or
non-const reference to a data member."

+
+  // Returns pointer to the visible region specified by visible_rect(). The
+  // memory is owned by VideoFrame object and must not be freed by the caller.
+  const uint8* visible_data(size_t plane) const;

[scherkus (not reviewing), 2014/10/20 19:30:36]

ditto

[magjed_chromium, 2014/10/22 15:16:39]

See above.

+  uint8* visible_data(size_t plane);
 
   // Returns the mailbox holder of the native texture wrapped by this frame.
   // Only valid to call if this is a NATIVE_TEXTURE frame. Before using the
   // mailbox, the caller must wait for the included sync point.
   const gpu::MailboxHolder* mailbox_holder() const;
 
   // Returns the shared-memory handle, if present
   base::SharedMemoryHandle shared_memory_handle() const;
 
 #if defined(OS_POSIX)
@@ skipping 110 matching lines @@
   uint32 release_sync_point_;
 
   const bool end_of_stream_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoFrame);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_FRAME_H_