Use explicit dependency injection for ClipboardMonitor

ext/bg/js/api.js

@@ -25,10 +25,6 @@ function apiAudioGetUrl(definition, source, optionsContext) {
     return _apiInvoke('audioGetUrl', {definition, source, optionsContext});
 }
 
-function apiClipboardGet() {
-    return _apiInvoke('clipboardGet');
-}
-
 function _apiInvoke(action, params={}) {
     const data = {action, params};
     return new Promise((resolve, reject) => {

ext/bg/js/backend.js

@@ -30,7 +30,7 @@ class Backend {
         this.translator = new Translator();
         this.anki = new AnkiNull();
         this.mecab = new Mecab();
-        this.clipboardMonitor = new ClipboardMonitor();
+        this.clipboardMonitor = new ClipboardMonitor({getClipboard: this._onApiClipboardGet.bind(this)});
         this.options = null;
         this.optionsSchema = null;
         this.defaultAnkiFieldTemplates = null;

ext/bg/js/clipboard-monitor.js

@@ -16,22 +16,23 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-/*global apiClipboardGet, jpIsStringPartiallyJapanese*/
+/*global jpIsStringPartiallyJapanese*/
 
 class ClipboardMonitor extends EventDispatcher {
-    constructor() {
+    constructor({getClipboard}) {
         super();
         this.timerId = null;
         this.timerToken = null;
         this.interval = 250;
         this.previousText = null;
+        this.getClipboard = getClipboard;
     }
 
     start() {
         this.stop();
 
         // The token below is used as a unique identifier to ensure that a new clipboard monitor
-        // hasn't been started during the await call. The check below the await apiClipboardGet()
+        // hasn't been started during the await call. The check below the await this.getClipboard()
         // call will exit early if the reference has changed.
         const token = {};
         const intervalCallback = async () => {
@@ -39,7 +40,7 @@ class ClipboardMonitor extends EventDispatcher {
 
             let text = null;
             try {
-                text = await apiClipboardGet();
+                text = await this.getClipboard();
             } catch (e) {
                 // NOP
             }

ext/bg/js/search.js

@@ -16,7 +16,7 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-/*global apiOptionsSet, apiTermsFind, Display, QueryParser, ClipboardMonitor*/
+/*global apiOptionsSet, apiTermsFind, apiClipboardGet, Display, QueryParser, ClipboardMonitor*/
 
 class DisplaySearch extends Display {
     constructor() {
@@ -38,7 +38,7 @@ class DisplaySearch extends Display {
         this.introVisible = true;
         this.introAnimationTimer = null;
 
-        this.clipboardMonitor = new ClipboardMonitor();
+        this.clipboardMonitor = new ClipboardMonitor({getClipboard: apiClipboardGet});
 
         this._onKeyDownIgnoreKeys = new Map([
             ['ANY_MOD', new Set([