Make PolyGerrit use Change's submittable field

Use the server provided value to determine if a change can be submitted.
This way, PolyGerrit does not rely on Labels, and respects the decision
taken by the server (which might be influenced by plugins).

Change-Id: Ic43cf3504d93aaebd689d64e7c97989d15221d73

polygerrit-ui/app/behaviors/rest-client-behavior/rest-client-behavior.html

@@ -151,7 +151,7 @@ limitations under the License.
       if (states.length || !opt_options) { return states; }
 
       // If no missing requirements, either active or ready to submit.
-      if (opt_options.readyToSubmit) {
+      if (change.submittable) {
         states.push('Ready to submit');
       } else {
         // Otherwise it is active.

polygerrit-ui/app/behaviors/rest-client-behavior/rest-client-behavior_test.html

@@ -93,28 +93,33 @@ limitations under the License.
       assert.deepEqual(statuses, []);
       assert.equal(statusString, '');
 
+      change.submittable = false;
       statuses = element.changeStatuses(change,
-          {readyToSubmit: false, includeDerived: true});
+          {includeDerived: true});
       assert.deepEqual(statuses, ['Active']);
 
       // With no missing labels
+      change.submittable = true;
       statuses = element.changeStatuses(change,
-          {readyToSubmit: true, includeDerived: true});
+          {includeDerived: true});
       statusString = element.changeStatusString(change);
       assert.deepEqual(statuses, ['Ready to submit']);
 
       change.mergeable = false;
+      change.submittable = true;
       statuses = element.changeStatuses(change,
-          {readyToSubmit: true, includeDerived: true});
+          {includeDerived: true});
       assert.deepEqual(statuses, ['Merge Conflict']);
 
       delete change.mergeable;
+      change.submittable = true;
       statuses = element.changeStatuses(change,
-          {readyToSubmit: true, includeDerived: true, mergeable: true});
+          {includeDerived: true, mergeable: true});
       assert.deepEqual(statuses, ['Ready to submit']);
 
+      change.submittable = true;
       statuses = element.changeStatuses(change,
-          {readyToSubmit: true, includeDerived: true, mergeable: false});
+          {includeDerived: true, mergeable: false});
       assert.deepEqual(statuses, ['Merge Conflict']);
     });
 

polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js

@@ -203,8 +203,7 @@
       },
       _changeStatuses: {
         type: String,
-        computed: '_computeChangeStatusChips(_change, _missingLabels, ' +
+        computed: '_computeChangeStatusChips(_change, _mergeable)',
-            '_mergeable)',
       },
       _commitCollapsed: {
         type: Boolean,
@@ -396,16 +395,11 @@
       return missingLabels;
     },
 
-    _readyToSubmit(missingLabels) {
+    _computeChangeStatusChips(change, mergeable) {
-      return missingLabels.length === 0;
-    },
-
-    _computeChangeStatusChips(change, missingLabels, mergeable) {
       // Show no chips until mergeability is loaded.
       if (mergeable === null || mergeable === undefined) { return []; }
 
       const options = {
-        readyToSubmit: this._readyToSubmit(missingLabels),
         includeDerived: true,
         mergeable: !!mergeable,
       };