Bug 1862450 - Made installer changes for dual browser extension to MacOS r=mhughes

Depends on D192478

Differential Revision: https://phabricator.services.mozilla.com/D192897

Author: nipunshukla21

browser/app/macbuild/Contents/Info.plist.in

@@ -232,6 +232,22 @@
 				<string>file</string>
 			</array>
 		</dict>
+		<dict>
+			<key>CFBundleURLName</key>
+			<string>Firefox Protocol</string>
+			<key>CFBundleURLSchemes</key>
+			<array>
+				<string>firefox</string>
+			</array>
+		</dict>
+		<dict>
+			<key>CFBundleURLName</key>
+			<string>Firefox Private Browsing Protocol</string>
+			<key>CFBundleURLSchemes</key>
+			<array>
+				<string>firefox-private</string>
+			</array>
+		</dict>
 	</array>
 	<key>CFBundleVersion</key>
 	<string>@MAC_BUNDLE_VERSION@</string>

browser/components/BrowserContentHandler.sys.mjs

@@ -543,14 +543,26 @@ nsBrowserContentHandler.prototype = {
         "private-window",
         false
       );
-      if (privateWindowParam) {
+      // Check for Firefox private browsing protocol handler here.
+      let privateProtocolFound = false;
+      let urlFlagIdx = cmdLine.findFlag("url", false);
+      if (urlFlagIdx > -1 && cmdLine.length > 1) {
+        privateProtocolFound = cmdLine
+          .getArgument(urlFlagIdx + 1)
+          .startsWith("firefox-private:");
+      }
+      if (privateWindowParam || privateProtocolFound) {
         let forcePrivate = true;
         let resolvedURI;
         if (!lazy.PrivateBrowsingUtils.enabled) {
           // Load about:privatebrowsing in a normal tab, which will display an error indicating
           // access to private browsing has been disabled.
           forcePrivate = false;
           resolvedURI = Services.io.newURI("about:privatebrowsing");
+        } else if (privateProtocolFound) {
+          // We can safely remove the flag and parameter now.
+          const privateProtocolURI = cmdLine.handleFlagWithParam("url", false);
+          resolvedURI = resolveURIInternal(cmdLine, privateProtocolURI);
         } else {
           resolvedURI = resolveURIInternal(cmdLine, privateWindowParam);
         }