Fix screen flickering for Windows platform…

webrtc/modules/desktop_capture/window_capturer_win.cc

Index: webrtc/modules/desktop_capture/window_capturer_win.cc
diff --git a/webrtc/modules/desktop_capture/window_capturer_win.cc b/webrtc/modules/desktop_capture/window_capturer_win.cc
index 54b2768aa803fe265d90a6b1f40884aafc795f88..dc31701790251743c0a8991be3388efc62592998 100644
--- a/webrtc/modules/desktop_capture/window_capturer_win.cc
+++ b/webrtc/modules/desktop_capture/window_capturer_win.cc
@@ -103,6 +103,8 @@ class WindowCapturerWin : public WindowCapturer {
 
   AeroChecker aero_checker_;
 
+  std::map<HWND, DesktopSize> window_size_map_;

[Sergey Ulanov, 2016/02/18 18:50:00]

Add a comment to explain why we need to cache the size.

[GeorgeZ, 2016/02/19 23:34:48]

Done.

+
   RTC_DISALLOW_COPY_AND_ASSIGN(WindowCapturerWin);
 };
 
@@ -128,7 +130,11 @@ bool WindowCapturerWin::SelectWindow(WindowId id) {
   if (!IsWindow(window) || !IsWindowVisible(window) || IsIconic(window))
     return false;
   window_ = window;
-  previous_size_.set(0, 0);
+  if (window_size_map_.count(window)) {
+    previous_size_ = window_size_map_[window];
+  } else {
+    previous_size_.set(0, 0);
+  }
   return true;
 }
 
@@ -170,6 +176,7 @@ void WindowCapturerWin::Capture(const DesktopRegion& region) {
     memset(frame->data(), 0, frame->stride() * frame->size().height());
 
     previous_size_ = frame->size();
+    window_size_map_[window_] = previous_size_;
     callback_->OnCaptureCompleted(frame);
     return;
   }
@@ -236,6 +243,7 @@ void WindowCapturerWin::Capture(const DesktopRegion& region) {
   ReleaseDC(window_, window_dc);
 
   previous_size_ = frame->size();
+  window_size_map_[window_] = previous_size_;
 
   frame->mutable_updated_region()->SetRect(
       DesktopRect::MakeSize(frame->size()));