Support global marks which select a tab

src/background/domains/global-mark.js

@@ -0,0 +1,19 @@
+export default class GlobalMark {
+  constructor(tabId, x, y) {
+    this.tabId0 = tabId;
+    this.x0 = x;
+    this.y0 = y;
+  }
+
+  get tabId() {
+    return this.tabId0;
+  }
+
+  get x() {
+    return this.x0;
+  }
+
+  get y() {
+    return this.y0;
+  }
+}