Bookmarks starts at root when cached path is permanent node & empty(iOS)

This CL makes Bookmarks ignore the cached path (and starts at root node)
when cached path of Bookmarks is a permanent node (Mobile Bookmarks,
Bookmarks Bar or Other Bookmarks) and is empty.  Egtest is modified
accordingly.

Bug: 571878
Change-Id: I68773b63e3f12a1ce1e1cf0842c2888dae92d568
Reviewed-on: https://chromium-review.googlesource.com/810185
Commit-Queue: Marti Wong <martiw@chromium.org>
Reviewed-by: Louis Romero <lpromero@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522415}

ios/chrome/browser/ui/bookmarks/bookmark_home_view_controller.mm

@@ -1067,19 +1067,20 @@ std::vector<GURL> GetUrlsToOpen(const std::vector<const BookmarkNode*>& nodes) {
   const BookmarkNode* node = bookmark_utils_ios::FindFolderById(
       self.bookmarks, [[mutablePath firstObject] longLongValue]);
   DCHECK(node);
-  if (node) {
-    BookmarkHomeViewController* controller =
-        [self createControllerWithRootFolder:node];
-    // We only scroll to the last viewing position for the leaf
-    // node.
-    if (mutablePath.count == 1 && pathCache.position) {
-      [controller
-          setCachedContentPosition:[NSNumber
-                                       numberWithFloat:pathCache.position]];
-    }
-    controller.isReconstructingFromCache = YES;
-    [self.navigationController pushViewController:controller animated:NO];
+  // if node is an empty permanent node, return.
+  if (node->empty() && IsPrimaryPermanentNode(node, self.bookmarks)) {
+    return;
+  }
+
+  BookmarkHomeViewController* controller =
+      [self createControllerWithRootFolder:node];
+  // Only scroll to the last viewing position for the leaf node.
+  if (mutablePath.count == 1 && pathCache.position) {
+    [controller
+        setCachedContentPosition:[NSNumber numberWithFloat:pathCache.position]];
   }
+  controller.isReconstructingFromCache = YES;
+  [self.navigationController pushViewController:controller animated:NO];
 }
 
 // Set up context bar for the new UI.

ios/chrome/browser/ui/bookmarks/bookmarks_new_generation_egtest.mm

@@ -2355,7 +2355,8 @@ id<GREYMatcher> TappableBookmarkNodeWithLabel(NSString* label) {
       assertWithMatcher:grey_sufficientlyVisible()];
 }
 
-- (void)testCachePositionIsRecreatedWhenNodeIsDeleted {
+// Verify root node is opened when cache position is deleted.
+- (void)testCachePositionIsResetWhenNodeIsDeleted {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitAndEnableFeature(kBookmarkNewGeneration);
 
@@ -2371,7 +2372,7 @@ id<GREYMatcher> TappableBookmarkNodeWithLabel(NSString* label) {
   [[EarlGrey selectElementWithMatcher:grey_accessibilityID(@"Folder 2")]
       performAction:grey_tap()];
 
-  // Close bookmarks
+  // Close bookmarks, it will store Folder 2 as the cache position.
   [[EarlGrey selectElementWithMatcher:BookmarksDoneButton()]
       performAction:grey_tap()];
 
@@ -2381,7 +2382,37 @@ id<GREYMatcher> TappableBookmarkNodeWithLabel(NSString* label) {
   // Reopen bookmarks.
   [BookmarksNewGenTestCase openBookmarks];
 
-  // Ensure the root node is opened, by verifying folders at this level.
+  // Ensure the root node is opened, by verifying Mobile Bookmarks is seen in a
+  // table cell.
+  [BookmarksNewGenTestCase verifyBookmarkFolderIsSeen:@"Mobile Bookmarks"];
+}
+
+// Verify root node is opened when cache position is a permanent node and is
+// empty.
+- (void)testCachePositionIsResetWhenNodeIsPermanentAndEmpty {
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitAndEnableFeature(kBookmarkNewGeneration);
+
+  [BookmarksNewGenTestCase setupStandardBookmarks];
+  [BookmarksNewGenTestCase openBookmarks];
+  [BookmarksNewGenTestCase openMobileBookmarks];
+
+  // Close bookmarks, it will store Mobile Bookmarks as the cache position.
+  [[EarlGrey selectElementWithMatcher:BookmarksDoneButton()]
+      performAction:grey_tap()];
+
+  // Delete all bookmarks and folders under Mobile Bookmarks.
+  [BookmarksNewGenTestCase removeBookmarkWithTitle:@"Folder 1.1"];
+  [BookmarksNewGenTestCase removeBookmarkWithTitle:@"Folder 1"];
+  [BookmarksNewGenTestCase removeBookmarkWithTitle:@"French URL"];
+  [BookmarksNewGenTestCase removeBookmarkWithTitle:@"Second URL"];
+  [BookmarksNewGenTestCase removeBookmarkWithTitle:@"First URL"];
+
+  // Reopen bookmarks.
+  [BookmarksNewGenTestCase openBookmarks];
+
+  // Ensure the root node is opened, by verifying Mobile Bookmarks is seen in a
+  // table cell.
   [BookmarksNewGenTestCase verifyBookmarkFolderIsSeen:@"Mobile Bookmarks"];
 }