Migrate gr-diff-comment to iron-a11y-keys

Bug: Issue 4198
Change-Id: I68ca64a9b0ef5cc9e83f19521529971d260fda55

polygerrit-ui/app/behaviors/keyboard-shortcut-behavior/keyboard-shortcut-behavior.html

@@ -56,6 +56,10 @@ limitations under the License.
     getKeyboardEvent(e) {
       return getKeyboardEvent(e);
     },
+
+    getRootTarget(e) {
+      return Polymer.dom(getKeyboardEvent(e)).rootTarget;
+    },
   };
 
   window.Gerrit = window.Gerrit || {};

polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.html

@@ -15,6 +15,7 @@ limitations under the License.
 -->
 
 <link rel="import" href="../../../bower_components/polymer/polymer.html">
+<link rel="import" href="../../../behaviors/keyboard-shortcut-behavior/keyboard-shortcut-behavior.html">
 <link rel="import" href="../../../bower_components/iron-autogrow-textarea/iron-autogrow-textarea.html">
 <link rel="import" href="../../shared/gr-textarea/gr-textarea.html">
 <link rel="import" href="../../shared/gr-button/gr-button.html">
@@ -241,8 +242,7 @@ limitations under the License.
           monospace
           disabled="{{disabled}}"
           rows="4"
-          text="{{_messageText}}"
-          on-keydown="_handleTextareaKeydown"></gr-textarea>
+          text="{{_messageText}}"></gr-textarea>
       <gr-formatted-text class="message"
           content="[[comment.message]]"
           no-trailing-margin="[[!comment.__draft]]"

polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.js

@@ -116,6 +116,15 @@
       '_calculateActionstoShow(showActions, isRobotComment)',
     ],
 
+    behaviors: [
+      Gerrit.KeyboardShortcutBehavior,
+    ],
+
+    keyBindings: {
+      'ctrl+enter meta+enter ctrl+s meta+s': '_handleSaveKey',
+      'esc': '_handleEsc',
+    },
+
     attached() {
       if (this.editing) {
         this.collapsed = false;
@@ -256,23 +265,17 @@
       return draft == null || draft.trim() == '';
     },
 
-    _handleTextareaKeydown(e) {
-      switch (e.keyCode) {
-        case 13: // 'enter'
-          if (this._messageText.length !== 0 && (e.metaKey || e.ctrlKey)) {
-            this._handleSave(e);
-          }
-          break;
-        case 27: // 'esc'
-          if (this._messageText.length === 0) {
-            this._handleCancel(e);
-          }
-          break;
-        case 83: // 's'
-          if (this._messageText.length !== 0 && e.ctrlKey) {
-            this._handleSave(e);
-          }
-          break;
+    _handleSaveKey(e) {
+      if (this._messageText.length) {
+        e.preventDefault();
+        this._handleSave(e);
+      }
+    },
+
+    _handleEsc(e) {
+      if (!this._messageText.length) {
+        e.preventDefault();
+        this._handleCancel(e);
       }
     },