Tree Data - Don't update pointers if range is within the same block

Summary:
Fixes a bug where we were trying to fix/update block pointers even when nothing changed across blocks.

Pair programmed with @[22701560:flarnie] :)

Reviewed By: mitermayer

Differential Revision: D9129494

fbshipit-source-id: 5b935371d30bdaa87849313ccd2c3c0f5be9facd

Author: niveditc

src/model/transaction/removeRangeFromContentState.js

@@ -307,7 +307,8 @@ const removeRangeFromContentState = (
 
   let updatedBlockMap = blockMap.merge(newBlocks).filter(block => !!block);
 
-  if (isExperimentalTreeBlock) {
+  // Only update tree block pointers if the range is across blocks
+  if (isExperimentalTreeBlock && startBlock !== endBlock) {
     updatedBlockMap = updateBlockMapLinks(
       updatedBlockMap,
       startBlock,