Double-encode file path for diff view

When navigating to diff view from change view, double-encode file path
to work around known pagejs library issue (see Issue 4255).

Bug: Issue 4474
Change-Id: I81bafcc86c4b2c450c92380eea52f315f5652b61

polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js

@@ -378,12 +378,13 @@
     },
 
     _computeDiffURL: function(changeNum, patchRange, path) {
+      // @see Issue 4255 regarding double-encoding.
       return '/c/' +
           encodeURIComponent(changeNum) +
           '/' +
           encodeURIComponent(this._patchRangeStr(patchRange)) +
           '/' +
-          path;
+          encodeURIComponent(encodeURIComponent(path));
     },
 
     _patchRangeStr: function(patchRange) {

polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.html

@@ -296,5 +296,19 @@ limitations under the License.
       assert.isFalse(element.diffs[0].hidden);
       diffStub.restore();
     });
+
+    test('file name should be double-escaped', function() {
+      element._files = [
+        {__path: 'my+file.txt'},
+      ];
+      element.changeNum = '42';
+      element.patchRange = {
+        basePatchNum: 'PARENT',
+        patchNum: '2',
+      };
+      flushAsynchronousOperations();
+      assert.equal(
+          element.$$('a').getAttribute('href'), '/c/42/2/my%252Bfile.txt');
+    });
   });
 </script>

polygerrit-ui/app/elements/core/gr-router/gr-router.js

@@ -134,12 +134,13 @@
       };
       // Don't allow diffing the same patch number against itself.
       if (params.basePatchNum === params.patchNum) {
+        // @see Issue 4255 regarding double-encoding.
         page.redirect('/c/' +
             encodeURIComponent(params.changeNum) +
             '/' +
             encodeURIComponent(params.patchNum) +
             '/' +
-            encodeURIComponent(params.path));
+            encodeURIComponent(encodeURIComponent(params.path)));
         return;
       }
       normalizePatchRangeParams(params);