Bookmark sync: Use random GUIDs as temporary server IDs

...instead of the actual GUID of the bookmark node.
This fixes a crash, see linked bug.
The problem is that right now, before the GUID-aware merge algorithm is
rolled out, bookmark GUIDs are not actually guaranteed to be unique.
This can result in two separate bookmark nodes getting assigned the
same server ID, resulting in a CHECK() crash.

This is an immediate fix for the crash; longer-term we need to make
sure that bookmark node GUIDs are actually guaranteed to be unique.

Bug: 1004205
Change-Id: Ic2e5e17b025b65e0739e6cb82a58053ff11209a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1864800
Commit-Queue: Marc Treib <treib@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706999}

components/sync_bookmarks/bookmark_model_merger.cc

@@ -470,7 +470,10 @@ void BookmarkModelMerger::ProcessLocalCreation(
   const bookmarks::BookmarkNode* node = parent->children()[index].get();
   DCHECK(!FindMatchingRemoteUpdateByGUID(node));
   DCHECK(base::IsValidGUID(node->guid()));
-  const std::string sync_id = node->guid();
+  // TODO(crbug.com/978430): Consider using |node->guid()| instead of generating
+  // a new random GUID. However, currently that can lead to crashes due to
+  // duplicate server IDs, see crbug.com/1004205.
+  const std::string sync_id = base::GenerateGUID();
   const int64_t server_version = syncer::kUncommittedVersion;
   const base::Time creation_time = base::Time::Now();
   const std::string& suffix = syncer::GenerateSyncableBookmarkHash(

components/sync_bookmarks/bookmark_model_observer_impl.cc

@@ -93,11 +93,12 @@ void BookmarkModelObserverImpl::BookmarkNodeAdded(
   // Similar to the directory implementation here:
   // https://cs.chromium.org/chromium/src/components/sync/syncable/mutable_entry.cc?l=237&gsn=CreateEntryKernel
   // Assign a temp server id for the entity. Will be overriden by the actual
-  // server id upon receiving commit response. As this value later populates the
-  // originator_client_item_id field in EntityData, which replaces the GUID in
-  // legacy clients, it is set to the node's actual GUID.
+  // server id upon receiving commit response.
   DCHECK(base::IsValidGUID(node->guid()));
-  const std::string sync_id = node->guid();
+  // TODO(crbug.com/978430): Consider using |node->guid()| instead of generating
+  // a new random GUID. However, currently that can lead to crashes due to
+  // duplicate server IDs, see crbug.com/1004205.
+  const std::string sync_id = base::GenerateGUID();
   const int64_t server_version = syncer::kUncommittedVersion;
   const base::Time creation_time = base::Time::Now();
   const sync_pb::UniquePosition unique_position =

components/sync_bookmarks/bookmark_model_observer_impl_unittest.cc

@@ -133,8 +133,12 @@ TEST_F(BookmarkModelObserverImplTest,
       bookmark_tracker()->GetEntitiesWithLocalChanges(kMaxEntries);
   ASSERT_THAT(local_changes.size(), 1U);
   EXPECT_THAT(local_changes[0]->bookmark_node(), Eq(bookmark_node));
-  EXPECT_THAT(local_changes[0]->metadata()->server_id(),
-              Eq(bookmark_node->guid()));
+  // TODO(crbug.com/978430): Consider using |node->guid()| instead of generating
+  // new random GUIDs as the temporary server ID, and then reinstate the
+  // following expectation. However, currently that can lead to crashes due to
+  // duplicate server IDs, see crbug.com/1004205.
+  // EXPECT_THAT(local_changes[0]->metadata()->server_id(),
+  //             Eq(bookmark_node->guid()));
 }
 
 TEST_F(BookmarkModelObserverImplTest,