[DesktopCapturer] FallbackDesktopCapturerWrapper and its tests

webrtc/modules/desktop_capture/shared_memory.cc

 /*
  *  Copyright (c) 2013 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.
  */
 
 #include "webrtc/modules/desktop_capture/shared_memory.h"
 
+#include "webrtc/base/checks.h"
+
 namespace webrtc {
 
 #if defined(WEBRTC_WIN)
 const SharedMemory::Handle SharedMemory::kInvalidHandle = NULL;
 #else
 const SharedMemory::Handle SharedMemory::kInvalidHandle = -1;
 #endif
 
 SharedMemory::SharedMemory(void* data, size_t size, Handle handle, int id)
   : data_(data),
     size_(size),
     handle_(handle),
     id_(id) {
 }
 
+SharedMemoryFactoryWrapper::SharedMemoryFactoryWrapper(
+    SharedMemoryFactory* factory) {
+  RTC_DCHECK(factory);
+  factory_ = factory;
+}
+
+SharedMemoryFactoryWrapper::~SharedMemoryFactoryWrapper() = default;
+
+//static
+std::unique_ptr<SharedMemoryFactory> SharedMemoryFactoryWrapper::Wrap(
+    const std::unique_ptr<SharedMemoryFactory>& factory) {
+  return std::unique_ptr<SharedMemoryFactory>(new SharedMemoryFactoryWrapper(
+      factory.get()));

[Jamie, 2017/02/15 18:43:49]

I don't think this is an acceptable use of unique_ptr. You're storing a bare
pointer to it with indefinite scope, so there's no guarantee it will remain
valid (the comment in the header is not enough of a guarantee).

It looks like you're only using this class in the FakeCapturer, in which case
I'd be a lot happier if this class moved there to make it clear that it's only
used in tests. I'd be even happier if you could move it there and also find a
way to make it comply with the semantics of unique_ptr.

[Hzj_jie, 2017/02/15 21:20:36]

This class is used in FallbackDesktopCapturerWrapper, which needs to share one
SharedMemoryFactory instance with two capturers. I may update the API of
SharedMemoryFactoryWrapper a little bit to avoid confusion.

+}
+
+std::unique_ptr<SharedMemory> SharedMemoryFactoryWrapper::CreateSharedMemory(
+    size_t size) {
+  return factory_->CreateSharedMemory(size);
+}
+
 }  // namespace webrtc