The origin initiating the external URI scheme launch.
The origin will be an empty string if the request is initiated by calling
CoreWebView2.Navigate on the external URI scheme. If a script initiates
the navigation, the InitiatingOrigin will be the top-level document's
Source, for example, if window.location is set to `"calculator://", the
InitiatingOrigin will be set to calculator://. If the request is initiated
from a child frame, the InitiatingOrigin will be the source of that child frame.
The origin initiating the external URI scheme launch. The origin will be an empty string if the request is initiated by calling CoreWebView2.Navigate on the external URI scheme. If a script initiates the navigation, the InitiatingOrigin will be the top-level document's Source, for example, if window.location is set to `"calculator://", the InitiatingOrigin will be set to calculator://. If the request is initiated from a child frame, the InitiatingOrigin will be the source of that child frame.