Remove bad const from disk_cache::Backend interface.

net/disk_cache/mem_backend_impl.h

Index: net/disk_cache/mem_backend_impl.h
diff --git a/net/disk_cache/mem_backend_impl.h b/net/disk_cache/mem_backend_impl.h
index 0ef7bbc239c84865f42d2693b7fb350136a0b708..6577084058d9706a346ff663c1b8a8e29cb92cb6 100644
--- a/net/disk_cache/mem_backend_impl.h
+++ b/net/disk_cache/mem_backend_impl.h
@@ -71,10 +71,10 @@ class NET_EXPORT_PRIVATE MemBackendImpl : public Backend {
   virtual int DoomEntry(const std::string& key,
                         const CompletionCallback& callback) OVERRIDE;
   virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomEntriesBetween(const base::Time initial_time,
-                                 const base::Time end_time,
+  virtual int DoomEntriesBetween(base::Time initial_time,
+                                 base::Time end_time,
                                  const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomEntriesSince(const base::Time initial_time,
+  virtual int DoomEntriesSince(base::Time initial_time,
                                const CompletionCallback& callback) OVERRIDE;
   virtual int OpenNextEntry(void** iter, Entry** next_entry,
                             const CompletionCallback& callback) OVERRIDE;