[Extensions] Fix a flaky declarativeContent API test.

DeclarativeContentApiTest.Overview was flaky because it did not
properly wait for page action icon visibility changes before
checking the visibility state.

Bug: 606574
Change-Id: Iaffc72868df454ceabb3c5d6447c9aa37820a5b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2229581Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776820}

chrome/browser/extensions/api/declarative_content/declarative_content_apitest.cc

@@ -9,6 +9,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
+#include "chrome/browser/extensions/chrome_extension_test_notification_observer.h"
 #include "chrome/browser/extensions/chrome_test_extension_loader.h"
 #include "chrome/browser/extensions/extension_action_manager.h"
 #include "chrome/browser/extensions/extension_action_test_util.h"
@@ -257,8 +258,7 @@ void DeclarativeContentApiTest::CheckBookmarkEvents(bool match_is_bookmarked) {
   EXPECT_EQ(!match_is_bookmarked, action->GetIsVisible(tab_id));
 }
 
-// Disabled due to flake. https://crbug.com/606574.
-IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest, DISABLED_Overview) {
+IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest, Overview) {
   ext_dir_.WriteManifest(kDeclarativeContentManifest);
   ext_dir_.WriteFile(
       FILE_PATH_LITERAL("background.js"),
@@ -295,14 +295,20 @@ IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest, DISABLED_Overview) {
       browser()->tab_strip_model()->GetWebContentsAt(0);
   const int tab_id = ExtensionTabUtil::GetTabId(tab);
 
-  NavigateInRenderer(tab, GURL("http://test1/"));
+  // Observer to track page action visibility. This helps avoid
+  // flakes by waiting to check visibility until there is an
+  // actual update to the page action.
+  ChromeExtensionTestNotificationObserver test_observer(browser());
 
+  NavigateInRenderer(tab, GURL("http://test1/"));
   // The declarative API should show the page action instantly, rather
   // than waiting for the extension to run.
+  test_observer.WaitForPageActionVisibilityChangeTo(1);
   EXPECT_TRUE(action->GetIsVisible(tab_id));
 
   // Make sure leaving a matching page unshows the page action.
   NavigateInRenderer(tab, GURL("http://not_checked/"));
+  test_observer.WaitForPageActionVisibilityChangeTo(0);
   EXPECT_FALSE(action->GetIsVisible(tab_id));
 
   // Insert a password field to make sure that's noticed.
@@ -311,10 +317,7 @@ IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest, DISABLED_Overview) {
       tab, "document.body.innerHTML = '<input type=\"password\">';"
            "document.body.offsetTop;"));
 
-  // Give the style match a chance to run and send back the matching-selector
-  // update.
-  ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
-
+  test_observer.WaitForPageActionVisibilityChangeTo(1);
   EXPECT_TRUE(action->GetIsVisible(tab_id))
       << "Adding a matching element should show the page action.";
 
@@ -324,10 +327,7 @@ IN_PROC_BROWSER_TEST_F(DeclarativeContentApiTest, DISABLED_Overview) {
       tab, "document.body.innerHTML = 'Hello world';"
            "document.body.offsetTop;"));
 
-  // Give the style match a chance to run and send back the matching-selector
-  // update.
-  ASSERT_TRUE(content::ExecuteScript(tab, std::string()));
-
+  test_observer.WaitForPageActionVisibilityChangeTo(0);
   EXPECT_FALSE(action->GetIsVisible(tab_id))
       << "Removing the matching element should hide the page action again.";
 }