Persist sessionStorage on disk.

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 487246aa0375a8e1542c800ee56a25e3667efc91..cf4c55f3ddefdceb52a97999d912d67b438a79ea 100644
--- a/content/public/browser/browser_context.h
+++ b/content/public/browser/browser_context.h
@@ -73,6 +73,13 @@ class CONTENT_EXPORT BrowserContext : public base::SupportsUserData {
   // Tells the HTML5 objects on this context to purge any uneeded memory.
   static void PurgeMemory(BrowserContext* browser_context);
 
+  // Controls if sessionStorage should be saved on disk. Returns true if
+  // updating the value succeeded, false if this function was called too
+  // late. Even if |save_session_storage_on_disk| is true, sessionStorage won't
+  // be saved if |IsOffTheRecord| returns true.
+  static bool SetSaveSessionStorageOnDisk(BrowserContext* browser_context,
+                                          bool save_session_storage_on_disk);
+
   virtual ~BrowserContext();
 
   // Returns the path of the directory where this context's data is stored.