Make <webview> use out-of-process iframe architecture.

content/browser/browser_plugin/browser_plugin_guest.h

 // 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.
 
 // A BrowserPluginGuest is the browser side of a browser <--> embedder
 // renderer channel. A BrowserPlugin (a WebPlugin) is on the embedder
 // renderer side of browser <--> embedder renderer communication.
 //
 // BrowserPluginGuest lives on the UI thread of the browser process. Any
 // messages about the guest render process that the embedder might be interested
@@ skipping 61 matching lines @@
 // A browser plugin guest provides functionality for WebContents to operate in
 // the guest role and implements guest-specific overrides for ViewHostMsg_*
 // messages.
 //
 // When a guest is initially created, it is in an unattached state. That is,
 // it is not visible anywhere and has no embedder WebContents assigned.
 // A BrowserPluginGuest is said to be "attached" if it has an embedder.
 // A BrowserPluginGuest can also create a new unattached guest via
 // CreateNewWindow. The newly created guest will live in the same partition,
 // which means it can share storage and can script this guest.
+//
+// Note: in --site-per-process, all IPCs sent out from this class will be
+// dropped on the floor since we don't have a BrowserPlugin.
 class CONTENT_EXPORT BrowserPluginGuest : public GuestHost,
                                           public WebContentsObserver {
  public:
   ~BrowserPluginGuest() override;
 
   // The WebContents passed into the factory method here has not been
   // initialized yet and so it does not yet hold a SiteInstance.
   // BrowserPluginGuest must be constructed and installed into a WebContents
   // prior to its initialization because WebContents needs to determine what
   // type of WebContentsView to construct on initialization. The content
@@ skipping 345 matching lines @@
   // Weak pointer used to ask GeolocationPermissionContext about geolocation
   // permission.
   base::WeakPtrFactory<BrowserPluginGuest> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserPluginGuest);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROWSER_PLUGIN_BROWSER_PLUGIN_GUEST_H_