Remove DesktopRegion parameter in DesktopCapturer::Capture.

webrtc/modules/desktop_capture/desktop_capturer.h

Index: webrtc/modules/desktop_capture/desktop_capturer.h
diff --git a/webrtc/modules/desktop_capture/desktop_capturer.h b/webrtc/modules/desktop_capture/desktop_capturer.h
index 778c93c63a0e638d75a110be7fa57c237f565a29..be948dbb6a5d56d575694faf7ae54ca816517920 100644
--- a/webrtc/modules/desktop_capture/desktop_capturer.h
+++ b/webrtc/modules/desktop_capture/desktop_capturer.h
@@ -66,13 +66,13 @@ class DesktopCapturer {
   virtual void SetSharedMemoryFactory(
       std::unique_ptr<SharedMemoryFactory> shared_memory_factory) {}
 
-  // Captures next frame. |region| specifies region of the capture target that
-  // should be fresh in the resulting frame. The frame may also include fresh
-  // data for areas outside |region|. In that case capturer will include these
-  // areas in updated_region() of the frame. |region| is specified relative to
-  // the top left corner of the capture target. Pending capture operations are
-  // canceled when DesktopCapturer is deleted.
-  virtual void Capture(const DesktopRegion& region) = 0;
+  // This is a legacy interface, consumers should call Capture2() function.
+  virtual void Capture(const DesktopRegion& region) { Capture2(); }
+
+  // Captures next frame, and involve callback provided by Start() function.
+  // Pending capture requests will be ignored once DesktopCapturer instance has

[Sergey Ulanov, 2016/10/11 18:42:41]

There is no way to issue a capture request after DesktopCapturer is deleted, so
this sentence is confusing. Keep the old wording? "Pending capture operations
are canceled when DesktopCapturer is deleted."

[Hzj_jie, 2016/10/11 19:32:05]

Done.

+  // been deleted.
+  virtual void Capture2() { Capture(DesktopRegion()); }

[Sergey Ulanov, 2016/10/11 18:42:41]

Call this Capture(). I don't think there are any issues with overloading the old
Capture(). 

[Hzj_jie, 2016/10/11 19:32:05]

That won't work, because http://www.stroustrup.com/bs_faq2.html#overloadderived.
I can surely add using DesktopCapturer::Capture in all derived classes. But
since the original Capture(const DesktopRegion&) will be removed anyway, we can
rename the Capture2 back to Capture when Capture(const DesktopRegion&) has been
removed.

[Sergey Ulanov, 2016/10/12 21:22:52]

This looks like a different issue. Here both overloads are in the same
interface.
I think overloading should work properly here.

 
   // Sets the window to be excluded from the captured image in the future
   // Capture calls. Used to exclude the screenshare notification window for