View-source URLs should use a separate SiteInstance in all cases.

content/browser/web_contents/render_view_host_manager.cc

Index: content/browser/web_contents/render_view_host_manager.cc
diff --git a/content/browser/web_contents/render_view_host_manager.cc b/content/browser/web_contents/render_view_host_manager.cc
index a11689187f7932b1b7873746bdbd253cd4471e70..62fec79d74de5e16ec285817f4bc86b6f9eb9689 100644
--- a/content/browser/web_contents/render_view_host_manager.cc
+++ b/content/browser/web_contents/render_view_host_manager.cc
@@ -488,6 +488,13 @@ SiteInstance* RenderViewHostManager::GetSiteInstanceForEntry(
     if (curr_site_instance->HasWrongProcessForURL(dest_url))
       return curr_site_instance->GetRelatedSiteInstance(dest_url);
 
+    // View-source URLs must use a new SiteInstance and BrowsingInstance.
+    // TODO(nasko): This is the same condition as later in the function. This
+    // should be taken into account when refactoring this method as part of
+    // http://crbug.com/123007.
+    if (entry.IsViewSourceMode())
+      return SiteInstance::CreateForURL(browser_context, dest_url);
+
     // Normally the "site" on the SiteInstance is set lazily when the load
     // actually commits. This is to support better process sharing in case
     // the site redirects to some other site: we want to use the destination