Fix window capturer to stop capturing when the target is minimized.

BUG=crbug.com/288205
R=alexeypa@chromium.org

Review URL: https://webrtc-codereview.appspot.com/2273005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4833 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/desktop_capture/window_capturer_win.cc

@@ -177,6 +177,12 @@ void WindowCapturerWin::Capture(const DesktopRegion& region) {
     return;
   }
 
+  // Stop capturing if the window has been minimized or hidden.
+  if (IsIconic(window_) || !IsWindowVisible(window_)) {
+    callback_->OnCaptureCompleted(NULL);
+    return;
+  }
+
   assert(window_);
 
   RECT rect;