Allow webview API in an unblessed extension process

chrome/renderer/extensions/dispatcher.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/extensions/dispatcher.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/debug/alias.h"
 #include "base/json/json_reader.h"
@@ skipping 1095 matching lines @@
   }
 
   if (context_type == Feature::BLESSED_EXTENSION_CONTEXT &&
       is_within_platform_app &&
       GetCurrentChannel() <= chrome::VersionInfo::CHANNEL_DEV &&
       CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableAppWindowControls)) {
     module_system->Require("windowControls");
   }
 
-  if (context_type == Feature::BLESSED_EXTENSION_CONTEXT) {
+  // Currently only platform apps and whitelisted component extensions support
+  // the <webview> tag, because the "denyWebView" module will affect the
+  // performance of DOM modifications (http://crbug.com/196453).
+  // We used to limit WebView to |BLESSED_EXTENSION_CONTEXT| within platform
+  // apps. An ext/app runs in a blessed extension context, if it is the active
+  // extension in the current process, in other words, if it is loaded in a top
+  // frame. To support webview in a non-frame extension, we have to allow
+  // unblessed extension context as well.
+  if (context_type == Feature::BLESSED_EXTENSION_CONTEXT ||
+      context_type == Feature::UNBLESSED_EXTENSION_CONTEXT) {
     // Note: setting up the WebView class here, not the chrome.webview API.
     // The API will be automatically set up when first used.
     if (extension->HasAPIPermission(APIPermission::kWebView)) {
       module_system->Require("webView");
       // TODO(mtomasz): Remove the Files app from the whitelist in M-31.
       // crbug.com/297936
       bool includeExperimental =
           GetCurrentChannel() <= chrome::VersionInfo::CHANNEL_DEV ||
           extension->id() == extension_misc::kIdentityApiUiAppId ||
           extension->id() == "hhaomjibdihmijegdhdafkllkbggdgoj";  // Files App.
@@ skipping 432 matching lines @@
     RenderView* background_view =
         ExtensionHelper::GetBackgroundPage(extension_id);
     if (background_view) {
       background_view->Send(new ExtensionHostMsg_EventAck(
           background_view->GetRoutingID()));
     }
   }
 }
 
 }  // namespace extensions