Wait for description propagation in TwoClientPrintersSyncTest.ConflictResolution.

Previously, the test ran all pending tasks, waited for all stores to be
equal, and then verified that the printer description was equal in all
stores.

It is better practice not to wait for all pending tasks to run, and
instead wait for the specific condition that we want to verify.

Bug: 810408
Change-Id: Ifa5fe80368285786664498991c82c1ccdecb5072
Reviewed-on: https://chromium-review.googlesource.com/1003224
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Nicolas Zea (slow) <zea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549522}

chrome/browser/sync/test/integration/two_client_printers_sync_test.cc

@@ -22,6 +22,9 @@ using printers_helper::GetPrinterStore;
 using printers_helper::PrintersMatchChecker;
 using printers_helper::RemovePrinter;
 
+constexpr char kOverwrittenDescription[] = "I should not show up";
+constexpr char kLatestDescription[] = "YAY!  More recent changes win!";
+
 class TwoClientPrintersSyncTest : public SyncTest {
  public:
   TwoClientPrintersSyncTest() : SyncTest(TWO_CLIENT) {}
@@ -31,6 +34,8 @@ class TwoClientPrintersSyncTest : public SyncTest {
   DISALLOW_COPY_AND_ASSIGN(TwoClientPrintersSyncTest);
 };
 
+}  // namespace
+
 IN_PROC_BROWSER_TEST_F(TwoClientPrintersSyncTest, NoPrinters) {
   ASSERT_TRUE(SetupSync());
 
@@ -114,24 +119,25 @@ IN_PROC_BROWSER_TEST_F(TwoClientPrintersSyncTest, ConflictResolution) {
   // Store 0 and 1 have 3 printers now.
   ASSERT_TRUE(PrintersMatchChecker().Wait());
 
-  std::string overwritten_message = "I should not show up";
   ASSERT_TRUE(
-      EditPrinterDescription(GetPrinterStore(1), 0, overwritten_message));
+      EditPrinterDescription(GetPrinterStore(1), 0, kOverwrittenDescription));
 
   // Wait for a non-zero period (200ms).
   base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(200));
 
-  std::string valid_message = "YAY!  More recent changes win!";
-  ASSERT_TRUE(EditPrinterDescription(GetPrinterStore(0), 0, valid_message));
-
-  // Run all pending tasks and wait until all clients have the same
-  // configuration.
-  content::RunAllTasksUntilIdle();
-  ASSERT_TRUE(PrintersMatchChecker().Wait());
-
-  // The more recent update should win.
-  EXPECT_EQ(valid_message,
-            GetPrinterStore(1)->GetConfiguredPrinters()[0].description());
+  ASSERT_TRUE(
+      EditPrinterDescription(GetPrinterStore(0), 0, kLatestDescription));
+
+  // Run tasks until the most recent update has been applied to all stores.
+  AwaitMatchStatusChangeChecker wait_latest_description_propagated(
+      base::BindRepeating([]() {
+        return GetPrinterStore(0)->GetConfiguredPrinters()[0].description() ==
+                   kLatestDescription &&
+               GetPrinterStore(1)->GetConfiguredPrinters()[0].description() ==
+                   kLatestDescription;
+      }),
+      "Description not propagated");
+  ASSERT_TRUE(wait_latest_description_propagated.Wait());
 }
 
 IN_PROC_BROWSER_TEST_F(TwoClientPrintersSyncTest, SimpleMerge) {
@@ -152,5 +158,3 @@ IN_PROC_BROWSER_TEST_F(TwoClientPrintersSyncTest, SimpleMerge) {
   EXPECT_EQ(4, GetPrinterCount(0));
   EXPECT_TRUE(AllProfilesContainSamePrinters());
 }
-
-}  // namespace