Fixes braille textarea output for empty lines

When arrowing by line (up/down) through a text area and encountering a blank line in braille

before:
- braille would not correctly clear the previous line contents
- e.g.
"Testing testing

one"


"Testing testing" would remain displayed even though the caret was on the second (blank) line.

after:
Arrowing by line results in
- blank display
- a blinking cursor over the first cell

Change-Id: I1cd770644f78c60e2c4cf4d074da5c048aff9e52
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2085155
Commit-Queue: David Tseng <dtseng@chromium.org>
Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746863}

chrome/browser/resources/chromeos/accessibility/chromevox/background/editing.js

@@ -56,7 +56,6 @@ editing.TextEditHandler = class {
       // A rich text field is one where selection gets placed on a DOM
       // descendant to a root text field. This is one of:
       // - content editables (detected via richly editable state)
-      // - the node is a textarea
       //
       // The only other editables we expect are all single line (including those
       // from ARC++).
@@ -245,6 +244,14 @@ const AutomationEditableText = class extends ChromeVoxEditableTextBase {
     }
     const startIndex = this.start - lineStart;
     const endIndex = this.end - lineStart;
+
+    // If the line is not the last line, and is empty, insert an explicit line
+    // break so that braille output is correctly cleared and has a position for
+    // a caret to be shown.
+    if (lineText == '' && lineIndex < this.lineBreaks_.length - 1) {
+      lineText = '\n';
+    }
+
     const spannable = new Spannable(lineText, new Output.NodeSpan(this.node_));
     ChromeVox.braille.write(
         new NavBraille({text: spannable, startIndex, endIndex}));

chrome/browser/resources/chromeos/accessibility/chromevox/background/editing_test.js

@@ -1361,3 +1361,23 @@ TEST_F('ChromeVoxEditingTest', 'SelectAll', function() {
         input.focus();
       });
 });
+
+TEST_F('ChromeVoxEditingTest', 'TextAreaBrailleEmptyLine', function() {
+  const mockFeedback = this.createMockFeedback();
+  this.runWithLoadedTree('<textarea></textarea>', function(root) {
+    const textarea = root.find({role: RoleType.TEXT_FIELD});
+    this.listenOnce(textarea, 'focus', function() {
+      this.listenOnce(textarea, 'valueChanged', function() {
+        mockFeedback.call(this.press(38 /* up arrow */)).expectBraille('\n');
+        mockFeedback.call(this.press(38 /* up arrow */)).expectBraille('two');
+        mockFeedback.call(this.press(38 /* up arrow */)).expectBraille('one');
+        mockFeedback.call(this.press(38 /* up arrow */)).expectBraille('\n');
+        mockFeedback.call(this.press(38 /* up arrow */))
+            .expectBraille('test mled')
+            .replay();
+      });
+    });
+    textarea.focus();
+    textarea.setValue('test\n\none\ntwo\n\nthree');
+  });
+});