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

components/guest_view/browser/guest_view_base.cc

Index: components/guest_view/browser/guest_view_base.cc
diff --git a/components/guest_view/browser/guest_view_base.cc b/components/guest_view/browser/guest_view_base.cc
index 201e08108e395fef62f7aa205fbb4cb6907a7c12..018cd36e61f249eca997bd4c5c56a15c88926d52 100644
--- a/components/guest_view/browser/guest_view_base.cc
+++ b/components/guest_view/browser/guest_view_base.cc
@@ -4,6 +4,7 @@
 
 #include "components/guest_view/browser/guest_view_base.h"
 
+#include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/guest_view/browser/guest_view_event.h"
@@ -18,6 +19,7 @@
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/content_switches.h"
 #include "content/public/common/page_zoom.h"
 #include "content/public/common/url_constants.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
@@ -558,6 +560,12 @@ void GuestViewBase::DidNavigateMainFrame(
     const content::FrameNavigateParams& params) {
   if (attached() && ZoomPropagatesFromEmbedderToGuest())
     SetGuestZoomLevelToMatchEmbedder();
+
+  // TODO(lazyboy): This breaks guest visibility in --site-per-process.

[Charlie Reis, 2015/05/22 23:44:30]

Can you explain a little more about the case that's broken in the TODO, to make
it easier to revisit and fix?

[lazyboy, 2015/05/26 16:32:54]

Done.

+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kSitePerProcess)) {
+    web_contents()->WasShown();
+  }
 }
 
 void GuestViewBase::ActivateContents(WebContents* web_contents) {