Do not collapse line numbers that are indicated in the URL

When users navigate to the diff view with a line number specified at the
end, depending on their context preference, the line might be in a
shared region that gets collapsed when the diff renders. With this
change, the location specified in the URL is prevented from being
collapsed by marking it as a "key" location.

Bug: Issue 5247
Change-Id: Ifd5827cd922b022cddb1601911a9ecea6a054f35

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 979f253..9a55bbe 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
@@ -646,6 +646,18 @@
       assert.equal(element.$.cursor.side, 'right');
     });
 
+    test('_getLineOfInterest', () => {
+      assert.isNull(element._getLineOfInterest({}));
+
+      let result = element._getLineOfInterest({lineNum: 12});
+      assert.equal(result.number, 12);
+      assert.isNotOk(result.leftSide);
+
+      result = element._getLineOfInterest({lineNum: 12, leftSide: true});
+      assert.equal(result.number, 12);
+      assert.isOk(result.leftSide);
+    });
+
     test('_onLineSelected', () => {
       const getUrlStub = sandbox.stub(Gerrit.Nav, 'getUrlForDiffById');
       const replaceStateStub = sandbox.stub(history, 'replaceState');