reorganize clone semantics, implement recently closed tabs history

src/profile/history/memory.rs

@@ -0,0 +1,24 @@
+mod closed;
+use closed::Closed;
+
+/// Reduce disk usage by cache Bookmarks index in memory
+pub struct Memory {
+    pub closed: Closed,
+}
+
+impl Default for Memory {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Memory {
+    // Constructors
+
+    /// Create new `Self`
+    pub fn new() -> Self {
+        Self {
+            closed: Closed::new(),
+        }
+    }
+}