[DesktopCapturer] FallbackDesktopCapturerWrapper and its tests

webrtc/modules/desktop_capture/shared_memory.cc

Index: webrtc/modules/desktop_capture/shared_memory.cc
diff --git a/webrtc/modules/desktop_capture/shared_memory.cc b/webrtc/modules/desktop_capture/shared_memory.cc
index 872116eec9f86d76bf9cdab2429d74a798f089b0..48547e8c8afb8811f588a668213eac50eb746136 100644
--- a/webrtc/modules/desktop_capture/shared_memory.cc
+++ b/webrtc/modules/desktop_capture/shared_memory.cc
@@ -10,6 +10,10 @@
 
 #include "webrtc/modules/desktop_capture/shared_memory.h"
 
+#include <utility>
+
+#include "webrtc/base/checks.h"
+
 namespace webrtc {
 
 #if defined(WEBRTC_WIN)
@@ -25,4 +29,29 @@ SharedMemory::SharedMemory(void* data, size_t size, Handle handle, int id)
     id_(id) {
 }
 
+SharedMemoryFactoryWrapper::SharedMemoryFactoryWrapper(
+    std::unique_ptr<SharedMemoryFactory> factory) {
+  RTC_DCHECK(factory);
+  owned_factory_ = std::move(factory);
+  shared_factory_ = owned_factory_.get();
+}
+
+SharedMemoryFactoryWrapper::SharedMemoryFactoryWrapper(
+    SharedMemoryFactory* factory) {
+  RTC_DCHECK(factory);
+  shared_factory_ = factory;
+}
+
+SharedMemoryFactoryWrapper::~SharedMemoryFactoryWrapper() = default;
+
+std::unique_ptr<SharedMemoryFactory> SharedMemoryFactoryWrapper::Wrap() const {
+  return std::unique_ptr<SharedMemoryFactory>(new SharedMemoryFactoryWrapper(

[Sergey Ulanov, 2017/02/15 23:08:43]

A better solution would be use a ref-counted holder for SharedMemoryFactory, so
the shared factory is destroyed only after all "wrappers" are destroyed.
SharedDesktopFrame works this way. There is nothing in DesktopCapturer interface
to guarantee that capturers stop using this factory when they are destroyed.
DesktopCapturer implementations are allowed to capture on a separate thread (see
DesktopCaptureProxy). Again this may not be a problem right now, but it should
be documented somewhere.

[Hzj_jie, 2017/02/16 01:57:07]

I have added comments for both SharedMemoryFactoryWrapper class and
CreateSharedMemory() function.
Considering this class is becoming complex, I added test cases.

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