Add command-line flag for tests to bypass the screenshare window picker.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index cbc6f330ce15279861032ced5e529e2810e503d1..ecfa8a913160e214d324f0fb695aa9614a5c0176 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -122,6 +122,13 @@ const char kAuthServerWhitelist[]           = "auth-server-whitelist";
 // computer startup and not by some user action.
 const char kAutoLaunchAtStartup[]           = "auto-launch-at-startup";
 
+// This flag makes Chrome auto-select the provided choice when an extension asks
+// permission to start desktop capture. Should only be used for tests. For
+// instance, --auto-select-desktop-capture-source="Entire screen" will
+// automatically select to share the entire screen in English locales.
+const char kAutoSelectDesktopCaptureSource[] =
+    "auto-select-desktop-capture-source";
+
 // Certificate Transparency: Uses the provided log(s) for checking Signed
 // Certificate Timestamps provided with certificates.
 // The switch's value is: