Add WebView PlzNavigate related fixes to extensions_browsertests harness.

extensions/shell/browser/shell_content_browser_client.h

Index: extensions/shell/browser/shell_content_browser_client.h
diff --git a/extensions/shell/browser/shell_content_browser_client.h b/extensions/shell/browser/shell_content_browser_client.h
index a87d36ecacdf4dbcc94d76e1c3d02ce408827fb4..c03b5de29344976fd7fbb7fe7c6016de8a9541a6 100644
--- a/extensions/shell/browser/shell_content_browser_client.h
+++ b/extensions/shell/browser/shell_content_browser_client.h
@@ -55,7 +55,11 @@ class ShellContentBrowserClient : public content::ContentBrowserClient {
       int plugin_process_id) override;
   void GetAdditionalAllowedSchemesForFileSystem(
       std::vector<std::string>* additional_schemes) override;
-  content::DevToolsManagerDelegate* GetDevToolsManagerDelegate() override;
+  content::DevToolsManagerDelegate* GetDevToolsManagerDelegate() override;
+  ScopedVector<content::NavigationThrottle> CreateThrottlesForNavigation(
+      content::NavigationHandle* navigation_handle) override;
+  std::unique_ptr<content::NavigationUIData> GetNavigationUIData(
+      content::NavigationHandle* navigation_handle) override;
 
  protected:
   // Subclasses may wish to provide their own ShellBrowserMainParts.