Make sure the default CSP is used for <webview> with PlzNavigate.

chrome/browser/extensions/chrome_extensions_browser_client.h

Index: chrome/browser/extensions/chrome_extensions_browser_client.h
diff --git a/chrome/browser/extensions/chrome_extensions_browser_client.h b/chrome/browser/extensions/chrome_extensions_browser_client.h
index 89477b1ed55b0a5fac9262d06eb431b87b3e3742..db78b8c9025ae202a629f188932655cb6a375499 100644
--- a/chrome/browser/extensions/chrome_extensions_browser_client.h
+++ b/chrome/browser/extensions/chrome_extensions_browser_client.h
@@ -122,6 +122,8 @@ class ChromeExtensionsBrowserClient : public ExtensionsBrowserClient {
       content::RenderFrameHost* frame,
       const content::BluetoothChooser::EventHandler& event_handler) override;
   bool IsActivityLoggingEnabled(content::BrowserContext* context) override;
+  extensions::ExtensionNavigationUIData* GetExtensionNavigationUIData(
+      net::URLRequest* request) override;
   KioskDelegate* GetKioskDelegate() override;
 
  private: