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

extensions/renderer/guest_view/extensions_guest_view_container.cc

Index: extensions/renderer/guest_view/extensions_guest_view_container.cc
diff --git a/extensions/renderer/guest_view/extensions_guest_view_container.cc b/extensions/renderer/guest_view/extensions_guest_view_container.cc
index 358f8001ceea5fd6fbf03aab0e399bc0f0379a87..772e9275d32dceb330e089d59d02862d59687cd5 100644
--- a/extensions/renderer/guest_view/extensions_guest_view_container.cc
+++ b/extensions/renderer/guest_view/extensions_guest_view_container.cc
@@ -4,7 +4,10 @@
 
 #include "extensions/renderer/guest_view/extensions_guest_view_container.h"
 
+#include "base/command_line.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/renderer/render_frame.h"
+#include "extensions/common/guest_view/extensions_guest_view_messages.h"
 #include "third_party/WebKit/public/web/WebScopedMicrotaskSuppression.h"
 #include "ui/gfx/geometry/size.h"
 
@@ -16,6 +19,11 @@ ExtensionsGuestViewContainer::ExtensionsGuestViewContainer(
       destruction_isolate_(nullptr),
       element_resize_isolate_(nullptr),
       weak_ptr_factory_(this) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kSitePerProcess)) {
+    // There is no BrowserPluginDelegate to wait for.
+    ready_ = true;
+  }
 }
 
 ExtensionsGuestViewContainer::~ExtensionsGuestViewContainer() {
@@ -42,6 +50,14 @@ void ExtensionsGuestViewContainer::RegisterDestructionCallback(
   destruction_isolate_ = isolate;
 }
 
+bool ExtensionsGuestViewContainer::OnMessage(const IPC::Message& message) {
+  if (message.type() != ExtensionsGuestViewMsg_ContentWindowReady::ID)
+    return false;
+
+  OnHandleCallback(message);
+  return true;
+}
+
 void ExtensionsGuestViewContainer::RegisterElementResizeCallback(
     v8::Local<v8::Function> callback,
     v8::Isolate* isolate) {