Introduce an IsMutable method on VideoFrameBuffer.

webrtc/common_video/video_frame_buffer.cc

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 71 matching lines @@
       return data_.get() + stride_y_ * height_;
     case kVPlane:
       return data_.get() + stride_y_ * height_ +
              stride_u_ * ((height_ + 1) / 2);
     default:
       RTC_NOTREACHED();
       return nullptr;
   }
 }
 
+bool I420Buffer::IsMutable() {
+  return HasOneRef();
+}
+
 uint8_t* I420Buffer::MutableData(PlaneType type) {
-  RTC_DCHECK(HasOneRef());
+  RTC_DCHECK(IsMutable());
   return const_cast<uint8_t*>(
       static_cast<const VideoFrameBuffer*>(this)->data(type));
 }
 
 int I420Buffer::stride(PlaneType type) const {
   switch (type) {
     case kYPlane:
       return stride_y_;
     case kUPlane:
       return stride_u_;
@@ skipping 33 matching lines @@
 
 NativeHandleBuffer::NativeHandleBuffer(void* native_handle,
                                        int width,
                                        int height)
     : native_handle_(native_handle), width_(width), height_(height) {
   RTC_DCHECK(native_handle != nullptr);
   RTC_DCHECK_GT(width, 0);
   RTC_DCHECK_GT(height, 0);
 }
 
+bool NativeHandleBuffer::IsMutable() {
+  return false;
+}
+
 int NativeHandleBuffer::width() const {
   return width_;
 }
 
 int NativeHandleBuffer::height() const {
   return height_;
 }
 
 const uint8_t* NativeHandleBuffer::data(PlaneType type) const {
   RTC_NOTREACHED();  // Should not be called.
@@ skipping 26 matching lines @@
       y_stride_(y_stride),
       u_stride_(u_stride),
       v_stride_(v_stride),
       no_longer_used_cb_(no_longer_used) {
 }
 
 WrappedI420Buffer::~WrappedI420Buffer() {
   no_longer_used_cb_();
 }
 
+// Data owned by creator; never mutable.
+bool WrappedI420Buffer::IsMutable() {
+  return false;
+}
+
 int WrappedI420Buffer::width() const {
   return width_;
 }
 
 int WrappedI420Buffer::height() const {
   return height_;
 }
 
 const uint8_t* WrappedI420Buffer::data(PlaneType type) const {
   switch (type) {
@@ skipping 57 matching lines @@
                            buffer->stride(kVPlane) * uv_offset_y + uv_offset_x;
   return new rtc::RefCountedObject<WrappedI420Buffer>(
       cropped_width, cropped_height,
       y_plane, buffer->stride(kYPlane),
       u_plane, buffer->stride(kUPlane),
       v_plane, buffer->stride(kVPlane),
       rtc::KeepRefUntilDone(buffer));
 }
 
 }  // namespace webrtc