text: // 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/browser/tab_contents/tab_util.h"
  
  #include "chrome/browser/profiles/profile.h"
  #include "chrome/browser/ui/webui/chrome_web_ui_controller_factory.h"
  #include "content/public/browser/browser_url_handler.h"
  #include "content/public/browser/render_view_host.h"
  #include "content/public/browser/site_instance.h"
  #include "content/public/browser/web_contents.h"
  #include "extensions/buildflags/buildflags.h"
  #include "url/gurl.h"
  
  #if BUILDFLAG(ENABLE_EXTENSIONS)
  #include "extensions/browser/extension_registry.h"
  #endif
  
  using content::RenderViewHost;
  using content::SiteInstance;
  using content::WebContents;
  
  namespace tab_util {
  
  content::WebContents* GetWebContentsByID(int render_process_id,
                                           int render_view_id) {
    RenderViewHost* render_view_host =
        RenderViewHost::FromID(render_process_id, render_view_id);
    if (!render_view_host)
      return NULL;
    return WebContents::FromRenderViewHost(render_view_host);
  }
  
  scoped_refptr<SiteInstance> GetSiteInstanceForNewTab(Profile* profile,
                                                       GURL url) {
    // Rewrite the |url| if necessary, to ensure that the SiteInstance is
    // associated with a |url| that will actually be loaded.  For example,
    // |url| set to chrome://newtab/ might actually result in a navigation to a
    // different URL like chrome-search://local-ntp/local-ntp.html
    content::BrowserURLHandler::GetInstance()->RewriteURLIfNecessary(&url,
                                                                     profile);
  
    // If |url| is a WebUI or extension, we set the SiteInstance up front so that
    // we don't end up with an extra process swap on the first navigation.
    if (ChromeWebUIControllerFactory::GetInstance()->UseWebUIForURL(profile, url))
      return SiteInstance::CreateForURL(profile, url);
  
  #if BUILDFLAG(ENABLE_EXTENSIONS)
    if (extensions::ExtensionRegistry::Get(profile)
            ->enabled_extensions()
            .GetHostedAppByURL(url))
      return SiteInstance::CreateForURL(profile, url);
  #endif
  
    // We used to share the SiteInstance for same-site links opened in new tabs,
    // to leverage the in-memory cache and reduce process creation.  It now
    // appears that it is more useful to have such links open in a new process,
    // so we create new tabs in a new BrowsingInstance.
    // Create a new SiteInstance for the |url| unless it is not desirable.
    if (!SiteInstance::ShouldAssignSiteForURL(url))
      return nullptr;
  
    return SiteInstance::CreateForURL(profile, url);
  }
  
  }  // namespace tab_util
  