Support jumping to next/previous file with comments via shortcut

Adds keyboard shortcuts to the diff view to navigate to the next or
previous file in the change's file list that has comments in the current
patch range.

Feature: Issue 5235
Change-Id: I1ad39089c1ac227e335093f25b72311f7e98b3f7

polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html

diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
index f6e4765..99dcd41 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view_test.html
@@ -584,5 +584,106 @@
       element.changeViewState = {diffMode: 'SIDE_BY_SIDE'};
       assert.equal(element._getDiffViewMode(), 'SIDE_BY_SIDE');
     });
+
+    suite('_loadCommentMap', function() {
+      test('empty', function(done) {
+        stub('gr-rest-api-interface', {
+          getDiffRobotComments: function() { return Promise.resolve({}); },
+          getDiffComments: function() { return Promise.resolve({}); },
+        });
+        element._loadCommentMap().then(function(map) {
+          assert.equal(Object.keys(map).length, 0);
+          done();
+        });
+      });
+
+      test('paths in patch range', function(done) {
+        stub('gr-rest-api-interface', {
+          getDiffRobotComments: function() { return Promise.resolve({}); },
+          getDiffComments: function() {
+            return Promise.resolve({
+              'path/to/file/one.cpp': [{patch_set: 3, message: 'lorem'}],
+              'path-to/file/two.py': [{patch_set: 5, message: 'ipsum'}],
+            });
+          },
+        });
+        element._changeNum = '42';
+        element._patchRange = {
+          basePatchNum: '3',
+          patchNum: '5',
+        };
+        element._loadCommentMap().then(function(map) {
+          assert.deepEqual(Object.keys(map),
+              ['path/to/file/one.cpp', 'path-to/file/two.py']);
+          done();
+        });
+      });
+
+      test('empty for paths outside patch range', function(done) {
+        stub('gr-rest-api-interface', {
+          getDiffRobotComments: function() { return Promise.resolve({}); },
+          getDiffComments: function() {
+            return Promise.resolve({
+              'path/to/file/one.cpp': [{patch_set: 'PARENT', message: 'lorem'}],
+              'path-to/file/two.py': [{patch_set: 2, message: 'ipsum'}],
+            });
+          },
+        });
+        element._changeNum = '42';
+        element._patchRange = {
+          basePatchNum: '3',
+          patchNum: '5',
+        };
+        element._loadCommentMap().then(function(map) {
+          assert.equal(Object.keys(map).length, 0);
+          done();
+        });
+      });
+    });
+
+    suite('_computeCommentSkips', function() {
+      test('empty file list', function() {
+        var commentMap = {
+          'path/one.jpg': true,
+          'path/three.wav': true,
+        };
+        var path = 'path/two.m4v';
+        var fileList = [];
+        var result = element._computeCommentSkips(commentMap, fileList, path);
+        assert.isNull(result.previous);
+        assert.isNull(result.next);
+      });
+
+      test('finds skips', function() {
+        var fileList = ['path/one.jpg', 'path/two.m4v', 'path/three.wav'];
+        var path = fileList[1];
+        var commentMap = {};
+        commentMap[fileList[0]] = true;
+        commentMap[fileList[1]] = false;
+        commentMap[fileList[2]] = true;
+
+        var result = element._computeCommentSkips(commentMap, fileList, path);
+        assert.equal(result.previous, fileList[0]);
+        assert.equal(result.next, fileList[2]);
+
+        commentMap[fileList[1]] = true;
+
+        result = element._computeCommentSkips(commentMap, fileList, path);
+        assert.equal(result.previous, fileList[0]);
+        assert.equal(result.next, fileList[2]);
+
+        path = fileList[0];
+
+        result = element._computeCommentSkips(commentMap, fileList, path);
+        assert.isNull(result.previous);
+        assert.equal(result.next, fileList[1]);
+
+        path = fileList[2];
+
+        result = element._computeCommentSkips(commentMap, fileList, path);
+        assert.equal(result.previous, fileList[1]);
+        assert.isNull(result.next);
+      });
+    });
   });
 </script>