Fix flakiness by removing GetLastActive from extension browser tests.

chrome/browser/extensions/extension_browsertest.h

Index: chrome/browser/extensions/extension_browsertest.h
diff --git a/chrome/browser/extensions/extension_browsertest.h b/chrome/browser/extensions/extension_browsertest.h
index 19141d5c679832c26ada7a4cfffc7d054aed2e23..070123eda16dfbe2e02a051de29f1d18c8b6436b 100644
--- a/chrome/browser/extensions/extension_browsertest.h
+++ b/chrome/browser/extensions/extension_browsertest.h
@@ -16,6 +16,7 @@
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_types.h"
+#include "content/public/browser/web_contents.h"
 
 namespace extensions {
 class Extension;
@@ -136,6 +137,17 @@ class ExtensionBrowserTest
   // crashed.
   bool WaitForExtensionCrash(const std::string& extension_id);
 
+  // Simulates a page calling window.open on an URL and waits for the
+  // navigation.
+  void OpenWindow(content::WebContents* contents,
+                  const GURL& url,
+                  bool newtab_process_should_equal_opener,
+                  content::WebContents** newtab_result);
+
+  // Simulates a page navigating itself to an URL and waits for the
+  // navigation.
+  void NavigateInRenderer(content::WebContents* contents, const GURL& url);
+
   // content::NotificationObserver
   virtual void Observe(int type,
                        const content::NotificationSource& source,