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

webrtc/modules/desktop_capture/desktop_geometry.cc

Index: webrtc/modules/desktop_capture/desktop_geometry.cc
diff --git a/webrtc/modules/desktop_capture/desktop_geometry.cc b/webrtc/modules/desktop_capture/desktop_geometry.cc
index 2af8cf826e4dc70193e58569b0e6824eddc140de..6c85d7a869408553fc2c132a5e466db8406413ab 100644
--- a/webrtc/modules/desktop_capture/desktop_geometry.cc
+++ b/webrtc/modules/desktop_capture/desktop_geometry.cc
@@ -54,5 +54,19 @@ void DesktopRect::Extend(int32_t left_offset,
   bottom_ += bottom_offset;
 }
 
+void DesktopRect::UnionWith(const DesktopRect& rect) {
+  if (is_empty()) {
+    left_ = rect.left();
+    top_ = rect.top();
+    right_ = rect.right();
+    bottom_ = rect.bottom();
+  } else {
+    left_ = std::min(left(), rect.left());
+    top_ = std::min(top(), rect.top());
+    right_ = std::max(right(), rect.right());
+    bottom_ = std::max(bottom(), rect.bottom());
+  }
+}
+
 }  // namespace webrtc