Portals: Attach TabHelpers when a Portal is created.

This CL adds a notification via WebContentsDelegate that
notifies the embedder that a new portal WebContents was created.

The chrome/ embedder then uses this notification in order to
attach TabHelpers to the newly created WebContents.

Bug: 865565

Change-Id: I3e39883a5869832e6e59be9db7ea9e88ab18cd64
Reviewed-on: https://chromium-review.googlesource.com/1197143Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Lucas Gadani <lfg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592498}

chrome/browser/ui/browser.cc

@@ -1717,6 +1717,10 @@ void Browser::WebContentsCreated(WebContents* source_contents,
   task_manager::WebContentsTags::CreateForTabContents(new_contents);
 }
 
+void Browser::PortalWebContentsCreated(WebContents* portal_web_contents) {
+  TabHelpers::AttachTabHelpers(portal_web_contents);
+}
+
 void Browser::RendererUnresponsive(
     WebContents* source,
     content::RenderWidgetHost* render_widget_host,

chrome/browser/ui/browser.h

@@ -636,6 +636,8 @@ class Browser : public TabStripModelObserver,
                           const std::string& frame_name,
                           const GURL& target_url,
                           content::WebContents* new_contents) override;
+  void PortalWebContentsCreated(
+      content::WebContents* portal_web_contents) override;
   void RendererUnresponsive(
       content::WebContents* source,
       content::RenderWidgetHost* render_widget_host,

content/browser/portal/portal.cc

@@ -9,6 +9,7 @@
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "content/public/common/content_switches.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "third_party/blink/public/common/features.h"
@@ -53,6 +54,9 @@ void Portal::Init(
       WebContents::FromRenderFrameHost(owner_render_frame_host_)
           ->GetBrowserContext());
   portal_contents_ = WebContents::Create(params);
+  WebContents::FromRenderFrameHost(owner_render_frame_host_)
+      ->GetDelegate()
+      ->PortalWebContentsCreated(portal_contents_.get());
 }
 
 void Portal::Navigate(const GURL& url) {

content/public/browser/web_contents_delegate.h

@@ -318,6 +318,9 @@ class CONTENT_EXPORT WebContentsDelegate {
                                   const GURL& target_url,
                                   WebContents* new_contents) {}
 
+  // Notifies the embedder that a Portal WebContents was created.
+  virtual void PortalWebContentsCreated(WebContents* portal_web_contents) {}
+
   // Notification that one of the frames in the WebContents is hung. |source| is
   // the WebContents that is hung, and |render_widget_host| is the
   // RenderWidgetHost that, while routing events to it, discovered the hang.