Make session restore understand that tabs have multiple SessionStorageNamespaces.

content/public/browser/browser_context.h

Index: content/public/browser/browser_context.h
diff --git a/content/public/browser/browser_context.h b/content/public/browser/browser_context.h
index 2acf4005eb33556610d2729c6167c50568232e7c..8eb2830c147170ae866467e6f6569d383581c212 100644
--- a/content/public/browser/browser_context.h
+++ b/content/public/browser/browser_context.h
@@ -65,8 +65,13 @@ class CONTENT_EXPORT BrowserContext : public base::SupportsUserData {
   static fileapi::FileSystemContext* GetFileSystemContext(
       BrowserContext* browser_context);
 
-  static content::StoragePartition* GetStoragePartition(
-      BrowserContext* browser_context, SiteInstance* site_instance);
+  static bool IsValidPartitionId(BrowserContext* browser_context,
+                                 const std::string& partition_id);
+  static StoragePartition* GetStoragePartition(BrowserContext* browser_context,
+                                               SiteInstance* site_instance);
+  static StoragePartition* GetStoragePartitionById(
+      BrowserContext* browser_context,
+      const std::string& partition_id);
   static void ForEachStoragePartition(
       BrowserContext* browser_context,
       const StoragePartitionCallback& callback);