DesktopRect::UnionWith() to extend current rect to cover the input rect

webrtc/modules/desktop_capture/desktop_geometry.h

Index: webrtc/modules/desktop_capture/desktop_geometry.h
diff --git a/webrtc/modules/desktop_capture/desktop_geometry.h b/webrtc/modules/desktop_capture/desktop_geometry.h
index 8e9b9183a82e9f781840da14ae977ecd442ba09e..1e0deda8930eccb4c5cb9b0980b7aa82de962bbc 100644
--- a/webrtc/modules/desktop_capture/desktop_geometry.h
+++ b/webrtc/modules/desktop_capture/desktop_geometry.h
@@ -124,6 +124,10 @@ class DesktopRect {
   // Finds intersection with |rect|.
   void IntersectWith(const DesktopRect& rect);
 
+  // Extends the rectangle to cover |rect|. If |this| is empty, replaces |this|
+  // with |rect|; if |rect| is empty, this function takes no effect.
+  void UnionWith(const DesktopRect& rect);
+
   // Adds (dx, dy) to the position of the rectangle.
   void Translate(int32_t dx, int32_t dy);
   void Translate(DesktopVector d) { Translate(d.x(), d.y()); };