Webview tag creation should be using storage partitions.

content/browser/browser_plugin/browser_plugin_embedder.cc

Index: content/browser/browser_plugin/browser_plugin_embedder.cc
diff --git a/content/browser/browser_plugin/browser_plugin_embedder.cc b/content/browser/browser_plugin/browser_plugin_embedder.cc
index abdde143de2e21e2cbeac70838a506ff710fb414..dd2f9191cbe352af87af40e1e8045872024c459b 100644
--- a/content/browser/browser_plugin/browser_plugin_embedder.cc
+++ b/content/browser/browser_plugin/browser_plugin_embedder.cc
@@ -21,6 +21,7 @@
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/web_contents_view.h"
 #include "content/public/common/url_constants.h"
+#include "net/base/escape.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 #include "ui/gfx/size.h"
 #include "ui/surface/transport_dib.h"
@@ -90,9 +91,23 @@ void BrowserPluginEmbedder::CreateGuest(RenderViewHost* render_view_host,
 
   const std::string& host =
       render_view_host->GetSiteInstance()->GetSiteURL().host();
+  std::string url_encoded_partition =
+      net::EscapeQueryParamValue(storage_partition_id, false);
+
+  // The SiteInstance of a given webview tag is based on the fact that it's a
+  // guest process in addition to which platform application the tag belongs to
+  // and what storage partition is in use, rather than the URL that the tag is
+  // being navigated to.

[awong, 2012/11/02 21:56:13]

Is this logic better here, or in a SiteInstance::CreateForGuest() function?

[nasko, 2012/11/03 00:36:24]

Since we use it only here, I'd rather not introduce new method with new concept
in SiteInstance. Trying to keep jam@'s spirit of simple content API :).

+  GURL guest_site(
+      base::StringPrintf("%s://%s/%s?%s", chrome::kGuestScheme,
+                         host.c_str(), persist_storage ? "persist" : "",

[awong, 2012/11/02 21:56:13]

put persist into constant?

[nasko, 2012/11/03 00:36:24]

If I put it into a constant, I have to do a lookup what the constant resolves
to. Since it is used only here, it seems more readable to me.

+                         url_encoded_partition.c_str()));
+  SiteInstance* guest_site_instance = SiteInstance::CreateForURL(
+      web_contents()->GetBrowserContext(), guest_site);
+
   guest_web_contents = WebContentsImpl::CreateGuest(
       web_contents()->GetBrowserContext(),
-      host,
+      guest_site_instance,
       instance_id,
       focused,
       visible);