[DesktopCapturer] FallbackDesktopCapturerWrapper and its tests

webrtc/modules/desktop_capture/shared_memory.h

Index: webrtc/modules/desktop_capture/shared_memory.h
diff --git a/webrtc/modules/desktop_capture/shared_memory.h b/webrtc/modules/desktop_capture/shared_memory.h
index 6e15f23f6b8a4a0429f2d4aa2c09228f447d03bc..f2c1d0428ec587e07803671b9ea18ac5b77a7754 100644
--- a/webrtc/modules/desktop_capture/shared_memory.h
+++ b/webrtc/modules/desktop_capture/shared_memory.h
@@ -76,6 +76,25 @@ class SharedMemoryFactory {
   RTC_DISALLOW_COPY_AND_ASSIGN(SharedMemoryFactory);
 };
 
+// Implementation to share a SharedMemoryFactory between DesktopCapturer
+// instances.
+class SharedMemoryFactoryWrapper : public SharedMemoryFactory {

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

Suggest putting this class in fallback_desktop_capturer_wrapper.cc, since it's
unlikely to be used anywhere else. 

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

Done.

+ public:
+  SharedMemoryFactoryWrapper(std::unique_ptr<SharedMemoryFactory> factory);
+  ~SharedMemoryFactoryWrapper() override;
+
+  // Creates a SharedMemoryFactory, which should not overlive current instance.
+  std::unique_ptr<SharedMemoryFactory> Wrap() const;
+
+  std::unique_ptr<SharedMemory> CreateSharedMemory(size_t size) override;
+
+ private:
+  SharedMemoryFactoryWrapper(SharedMemoryFactory* factory);
+
+  std::unique_ptr<SharedMemoryFactory> owned_factory_;
+  SharedMemoryFactory* shared_factory_ = nullptr;
+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_SHARED_MEMORY_H_