Bug 1646289 - [CDP] Share unique TabTarget id with WebDriver. r=webdriver-reviewers,jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D139316

remote/cdp/targets/TabTarget.jsm

@@ -13,6 +13,7 @@ const { XPCOMUtils } = ChromeUtils.import(
 
 XPCOMUtils.defineLazyModuleGetters(this, {
   RemoteAgent: "chrome://remote/content/components/RemoteAgent.jsm",
+  TabManager: "chrome://remote/content/shared/TabManager.jsm",
   TabSession: "chrome://remote/content/cdp/sessions/TabSession.jsm",
   Target: "chrome://remote/content/cdp/targets/Target.jsm",
 });
@@ -37,6 +38,10 @@ class TabTarget extends Target {
 
     this.browser = browser;
 
+    // The tab target uses a unique id as shared with WebDriver to reference
+    // a specific tab.
+    this.id = TabManager.getIdForBrowser(browser);
+
     // Define the HTTP path to query this target
     this.path = `/devtools/page/${this.id}`;