Fix flakiness in AccessibilityFeaturesApiTest.Set tests

The problem with tests was that spoken feedback was getting enabled just
before loading the test extension. This would cause two extensions being
loaded: ChromeVox extension (which gets loaded when spoken feedback is
enabled) and the test extension. This is situation extension API tests
don't handle well. They wait for the test extension to get loaded by
waiting for any EXTENSION_LOADED notification. If the ChromeVox extension
got loaded before the test extension, the extension api test would continue
running too soon (before the test extension was loaded), and fail when the
test extension could not be found in extension set by its path.

To avoid that, keep spoken feedback disabled at the start of the test
(which should ensure that the ChromeVox extension doesn't get loaded while
the test extension is loading).

BUG=384266

Review URL: https://codereview.chromium.org/331383002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278269 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/extensions/accessibility_features_apitest.cc

@@ -161,15 +161,15 @@ class AccessibilityFeaturesApiTest : public ExtensionApiTest,
   }
 };
 
-// Disabled now as this test is being flaky, see http://crbug.com/384266.
-INSTANTIATE_TEST_CASE_P(
-    DISABLED_AccessibilityFeatureaApiTestInstantiatePermission,
+INSTANTIATE_TEST_CASE_P(AccessibilityFeatureaApiTestInstantiatePermission,
                         AccessibilityFeaturesApiTest,
                         testing::Bool());
 
 // Tests that an extension with read permission can read accessibility features
 // state, while an extension that doesn't have the permission cannot.
 IN_PROC_BROWSER_TEST_P(AccessibilityFeaturesApiTest, Get) {
+  // WARNING: Make sure that spoken feedback is not among enabled_features
+  // (see |Set| test for the reason).
   std::vector<std::string> enabled_features;
   enabled_features.push_back("largeCursor");
   enabled_features.push_back("stickyKeys");
@@ -188,19 +188,27 @@ IN_PROC_BROWSER_TEST_P(AccessibilityFeaturesApiTest, Get) {
   ASSERT_TRUE(GenerateTestArg(
       "getterTest", enabled_features, disabled_features, &test_arg));
   EXPECT_TRUE(
-      RunPlatformAppTestWithArg(GetTestExtensionPath(), test_arg.c_str()));
+      RunPlatformAppTestWithArg(GetTestExtensionPath(), test_arg.c_str()))
+      << message_;
 }
 
 // Tests that an extension with modify permission can modify accessibility
 // features, while an extension that doesn't have the permission can't.
 IN_PROC_BROWSER_TEST_P(AccessibilityFeaturesApiTest, Set) {
+  // WARNING: Make sure that spoken feedback does not get enabled at this point
+  // (before the test app is loaded), as that may break the test:
+  // |RunPlatformAppTestWithArg| waits for the test extension to load by
+  // waiting for EXTENSION_LOADED notification to be observed. It also assumes
+  // that there is only one extension being loaded during this time (it finishes
+  // when the first notification is seen). Enabling spoken feedback here would
+  // break this assumption as it would induce loading of ChromeVox extension.
   std::vector<std::string> enabled_features;
-  enabled_features.push_back("spokenFeedback");
   enabled_features.push_back("stickyKeys");
   enabled_features.push_back("autoclick");
   enabled_features.push_back("virtualKeyboard");
 
   std::vector<std::string> disabled_features;
+  disabled_features.push_back("spokenFeedback");
   disabled_features.push_back("largeCursor");
   disabled_features.push_back("highContrast");
   disabled_features.push_back("screenMagnifier");
@@ -214,7 +222,8 @@ IN_PROC_BROWSER_TEST_P(AccessibilityFeaturesApiTest, Set) {
 
   // The test extension attempts to flip all feature values.
   ASSERT_TRUE(
-      RunPlatformAppTestWithArg(GetTestExtensionPath(), test_arg.c_str()));
+      RunPlatformAppTestWithArg(GetTestExtensionPath(), test_arg.c_str()))
+      << message_;
 
   // The test tries to flip the feature states.
   if (ShouldModifyingFeatureSucceed()) {
@@ -227,6 +236,8 @@ IN_PROC_BROWSER_TEST_P(AccessibilityFeaturesApiTest, Set) {
 // Tests that an extension with read permission is notified when accessibility
 // features change.
 IN_PROC_BROWSER_TEST_F(AccessibilityFeaturesApiTest, ObserveFeatures) {
+  // WARNING: Make sure that spoken feedback is not among enabled_features
+  // (see |Set| test for the reason).
   std::vector<std::string> enabled_features;
   enabled_features.push_back("largeCursor");
   enabled_features.push_back("stickyKeys");
@@ -248,7 +259,8 @@ IN_PROC_BROWSER_TEST_F(AccessibilityFeaturesApiTest, ObserveFeatures) {
   // running when the accessibility features are flipped; oterwise, the
   // extension may not see events.
   ASSERT_TRUE(RunPlatformAppTestWithArg(kTestExtensionPathReadPermission,
-                                        test_arg.c_str()));
+                                        test_arg.c_str()))
+      << message_;
 
   // This should flip all features.
   ASSERT_TRUE(