move waitFor and get to BaseObservableValue

src/observable/ObservableValue.js

@@ -25,6 +25,17 @@ export class BaseObservableValue extends BaseObservable {
         }
     }
 
+    get() {
+        throw new Error("unimplemented");
+    }
+
+    waitFor(predicate) {
+        if (predicate(this.get())) {
+            return new ResolvedWaitForHandle(Promise.resolve(this.get()));
+        } else {
+            return new WaitForHandle(this, predicate);
+        }
+    }
 }
 
 class WaitForHandle {
@@ -81,14 +92,6 @@ export class ObservableValue extends BaseObservableValue {
             this.emit(this._value);
         }
     }
-
-    waitFor(predicate) {
-        if (predicate(this.get())) {
-            return new ResolvedWaitForHandle(Promise.resolve(this.get()));
-        } else {
-            return new WaitForHandle(this, predicate);
-        }
-    }
 }
 
 export function tests() {

src/ui/web/dom/OnlineStatus.js

@@ -31,7 +31,7 @@ export class OnlineStatus extends BaseObservableValue {
         this.emit(true);
     }
 
-    get value() {
+    get() {
         return navigator.onLine;
     }