Implement inline signin with iframe

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index cf19a3aeea08e14d4a3646a5f236d74021053958..b1c825539541eac44fb1cad5fe4b38d88a885ec2 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -802,6 +802,10 @@ void ChromeContentBrowserClient::GetStoragePartitionConfigForSite(
       *in_memory = false;
       partition_name->clear();
     }
+  } else if (site.GetOrigin().spec() == kChromeUIChromeSigninURL) {
+    // Chrome signin page has an embedded iframe of extension and web content,
+    // thus it must be isolated from other webUI pages.
+    *partition_domain = chrome::kChromeUIChromeSigninHost;
   }
 
   // Assert that if |can_be_default| is false, the code above must have found a