Place <webview> tag behind a flag.

chrome/renderer/extensions/dispatcher.cc

Index: chrome/renderer/extensions/dispatcher.cc
diff --git a/chrome/renderer/extensions/dispatcher.cc b/chrome/renderer/extensions/dispatcher.cc
index eeb26f1bfa607de3166f171b04d09c49d26e3d46..bf2ec590ef738ea142f9ca74b630a3f30b0eb1e7 100644
--- a/chrome/renderer/extensions/dispatcher.cc
+++ b/chrome/renderer/extensions/dispatcher.cc
@@ -803,6 +803,9 @@ void Dispatcher::DidCreateScriptContext(
     module_system->Require("platformApp");
 
   if (context_type == Feature::BLESSED_EXTENSION_CONTEXT &&
+      (CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableWebView) ||
+      (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableBrowserPluginForAllViewTypes))) &&
       extension->HasAPIPermission(APIPermission::kWebView)) {
     module_system->Require("webview");
   }