More caution when removing all ranges in blur handler

Summary:
Now we only do it if the current selection is still in the wrong element..

Should mitigate #1190.

Reviewed By: flarnie

Differential Revision: D5570526

fbshipit-source-id: 0b5b88542993773d71db0fffeb09c1b5c65c627e

src/component/handlers/edit/editOnBlur.js

@@ -14,12 +14,14 @@
 
 import type DraftEditor from 'DraftEditor.react';
 
-var EditorState = require('EditorState');
-var UserAgent = require('UserAgent');
+const DraftFeatureFlags = require('DraftFeatureFlags');
+const EditorState = require('EditorState');
+const UserAgent = require('UserAgent');
 
-var getActiveElement = require('getActiveElement');
+const containsNode = require('containsNode');
+const getActiveElement = require('getActiveElement');
 
-var isWebKit = UserAgent.isEngine('WebKit');
+const isWebKit = UserAgent.isEngine('WebKit');
 
 function editOnBlur(editor: DraftEditor, e: SyntheticEvent): void {
   // Webkit has a bug in which blurring a contenteditable by clicking on
@@ -29,7 +31,16 @@ function editOnBlur(editor: DraftEditor, e: SyntheticEvent): void {
   // to force it when blurring occurs within the window (as opposed to
   // clicking to another tab or window).
   if (isWebKit && getActiveElement() === document.body) {
-    global.getSelection().removeAllRanges();
+    const selection = global.getSelection();
+    const editorNode = editor.refs.editor;
+    if (
+      !DraftFeatureFlags.draft_cautious_range_removal_on_blur ||
+      selection.rangeCount === 1 &&
+      containsNode(editorNode, selection.anchorNode) &&
+      containsNode(editorNode, selection.focusNode)
+    ) {
+      selection.removeAllRanges();
+    }
   }
 
   var editorState = editor._latestEditorState;

src/component/utils/DraftFeatureFlags-core.js

@@ -14,6 +14,7 @@
 
 var DraftFeatureFlags = {
   draft_accept_selection_after_refocus: false,
+  draft_cautious_range_removal_on_blur: false,
   draft_killswitch_allow_nontextnodes: false,
   draft_segmented_entities_behavior: false,
 };