Diagnostics: Support observable with multiple responses

Bug: 1125150
Test: browser_tests --gtest_filter=DiagnosticsApp*
Change-Id: I98fc3ffa4818417fc02a92407dbf35eff8c8f601
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2424715
Commit-Queue: Zentaro Kavanagh <zentaro@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809871}

chrome/test/data/webui/chromeos/diagnostics/diagnostics_test.js

@@ -383,6 +383,56 @@ suite('FakeObservablesTest', () => {
     observables.trigger('ObserveFoo_OnFooUpdated');
     return resolver.promise;
   });
+
+  test('TwoResults', () => {
+    observables.register('ObserveFoo_OnFooUpdated');
+    /** @type !Array<string> */
+    const expected = ['bar1', 'bar2'];
+    observables.setObservableData('ObserveFoo_OnFooUpdated', expected);
+
+    // The first call will get 'bar1', and the second 'bar2'.
+    let resolver = new PromiseResolver();
+    const expectedCallCount = 2;
+    let callCount = 0;
+    observables.observe('ObserveFoo_OnFooUpdated', (foo) => {
+      assertEquals(expected[callCount % expected.length], foo);
+      callCount++;
+      if (callCount === expectedCallCount) {
+        resolver.resolve();
+      }
+    });
+
+    // Trigger the observer twice.
+    observables.trigger('ObserveFoo_OnFooUpdated');
+    observables.trigger('ObserveFoo_OnFooUpdated');
+    return resolver.promise;
+  });
+
+  test('ObservableDataWraps', () => {
+    observables.register('ObserveFoo_OnFooUpdated');
+    /** @type !Array<string> */
+    const expected = ['bar1', 'bar2'];
+    observables.setObservableData('ObserveFoo_OnFooUpdated', expected);
+
+    // With 3 calls and 2 observable values the response should cycle
+    // 'bar1', 'bar2', 'bar1'
+    let resolver = new PromiseResolver();
+    const expectedCallCount = 3;
+    let callCount = 0;
+    observables.observe('ObserveFoo_OnFooUpdated', (foo) => {
+      assertEquals(expected[callCount % expected.length], foo);
+      callCount++;
+      if (callCount === expectedCallCount) {
+        resolver.resolve();
+      }
+    });
+
+    // Trigger the observer three times.
+    observables.trigger('ObserveFoo_OnFooUpdated');
+    observables.trigger('ObserveFoo_OnFooUpdated');
+    observables.trigger('ObserveFoo_OnFooUpdated');
+    return resolver.promise;
+  });
 });
 
 

chromeos/components/diagnostics_ui/resources/fake_observables.js

@@ -37,9 +37,6 @@ class FakeObservableState {
 
   /** @param {!Array<!T>} observations */
   setObservableData(observations) {
-    // TODO(zentaro): Fully support multiple observations.
-    assert(observations.length == 1);
-
     this.observations_ = observations;
     this.index_ = 0;
   }