[iOS][EG2] Add sync to some ChromeEarlGrey operations.

Added sync after some ChromeEarlGrey operations where a UI change in
app might be triggered. This should eliminate undesirable racing
conditions before UI change finishes at app. TabUsageRecorderTestCase
is an example and this CL fixes it.

Bug: 1034196, 1033879
Change-Id: Ib260414371b832eed517d8bf72b2ee0c10f5cfd7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1970914
Commit-Queue: Zhaoyang Li <zhaoyangli@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726550}

ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm

@@ -266,10 +266,6 @@ void SwitchToNormalMode() {
   SwitchToNormalMode();
 
   [ChromeEarlGrey selectTabAtIndex:0];
-#if defined(CHROME_EARL_GREY_2)
-  // TODO(crbug.com/1033879): Remove this timer once the sync is fixed.
-  base::test::ios::SpinRunLoopWithMinDelay(base::TimeDelta::FromSeconds(1));
-#endif
   [ChromeEarlGrey waitForWebStateContainingText:kURL1FirstWord];
 
   // Verify that one page-load count has been recorded. It should contain two
@@ -747,10 +743,6 @@ void SwitchToNormalMode() {
   SwitchToNormalMode();
 
   [ChromeEarlGrey selectTabAtIndex:tabIndex];
-#if defined(CHROME_EARL_GREY_2)
-  // TODO(crbug.com/1033879): Remove this timer once the sync is fixed.
-  base::test::ios::SpinRunLoopWithMinDelay(base::TimeDelta::FromSeconds(1));
-#endif
   [ChromeEarlGrey waitForWebStateContainingText:"arrived"];
 
   // Verify that one page-load count has been recorded.  It should contain a

ios/chrome/test/earl_grey/chrome_earl_grey.mm

@@ -192,6 +192,9 @@ GREY_STUB_CLASS_IN_APP_MAIN_QUEUE(ChromeEarlGreyAppInterface)
 
 - (void)selectTabAtIndex:(NSUInteger)index {
   [ChromeEarlGreyAppInterface selectTabAtIndex:index];
+  // Tab changes are initiated through |WebStateList|. Need to wait its
+  // obeservers to complete UI changes at app.
+  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
 }
 
 - (BOOL)isIncognitoMode {
@@ -200,6 +203,9 @@ GREY_STUB_CLASS_IN_APP_MAIN_QUEUE(ChromeEarlGreyAppInterface)
 
 - (void)closeTabAtIndex:(NSUInteger)index {
   [ChromeEarlGreyAppInterface closeTabAtIndex:index];
+  // Tab changes are initiated through |WebStateList|. Need to wait its
+  // obeservers to complete UI changes at app.
+  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
 }
 
 - (NSUInteger)mainTabCount {
@@ -277,6 +283,9 @@ GREY_STUB_CLASS_IN_APP_MAIN_QUEUE(ChromeEarlGreyAppInterface)
 
 - (void)closeAllTabs {
   [ChromeEarlGreyAppInterface closeAllTabs];
+  // Tab changes are initiated through |WebStateList|. Need to wait its
+  // obeservers to complete UI changes at app.
+  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
 }
 
 - (void)waitForPageToFinishLoading {