Add ctrl+s as keyboard shortcut to save comment draft

Shortcut only functions while editing the actual text area of the
comment. This makes sense, as one should have to save each individual
comment as a draft. This also mimics the current behavior of GWT UI.

Bug: Issue 3848
Change-Id: I7037d3dbdc5dae3048fcae580ed09c41e54f0669

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

diff --git a/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.js b/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.js
index 1b30bde..07badbf 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment.js
@@ -198,8 +198,15 @@
     },
 
     _handleTextareaKeydown: function(e) {
-      if (e.keyCode == 27) {  // 'esc'
-        this._handleCancel(e);
+      switch (e.keyCode) {
+        case 27: // 'esc'
+          this._handleCancel(e);
+          break;
+        case 83: // 's'
+          if (e.ctrlKey) {
+            this._handleSave(e);
+          }
+          break;
       }
     },
 

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

diff --git a/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment_test.html b/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment_test.html
index fcf8b41..bddc3ab 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-comment/gr-diff-comment_test.html
@@ -211,6 +211,18 @@
       MockInteractions.pressAndReleaseKeyOn(element.$.editTextarea, 27); // esc
     });
 
+    test('ctrl+s saves comment', function(done) {
+      var stub = sinon.stub(element, 'save', function() {
+        assert.isTrue(stub.called);
+        stub.restore();
+        done();
+      });
+      element._messageText = 'is that the horse from horsing around??';
+      MockInteractions.pressAndReleaseKeyOn(
+        element.$.editTextarea.textarea,
+        83, 'ctrl');  // 'ctrl + s'
+    });
+
     test('draft saving/editing', function(done) {
       var fireStub = sinon.stub(element, 'fire');