Textarea: Remove unnecessary code for non-last BRs

ValueWithHardLineBreaks() assumes InnerEditor elements don't contain
<br>s other than the last child. DCHECK()s check the assumption, and
don't need to emit LFs for non-last <br>s.

This CL should not change any behavior.

Change-Id: Ifed37f35e01fb34c95c31d966066c25a86cdce81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462742
Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815481}

third_party/blink/renderer/core/html/forms/text_control_element.cc

@@ -952,8 +952,6 @@ String TextControlElement::ValueWithHardLineBreaks() const {
     for (Node& node : NodeTraversal::DescendantsOf(*inner_text)) {
       if (IsA<HTMLBRElement>(node)) {
         DCHECK_EQ(&node, inner_text->lastChild());
-        if (&node != inner_text->lastChild())
-          result.Append(kNewlineCharacter);
       } else if (auto* text_node = DynamicTo<Text>(node)) {
         String data = text_node->data();
         unsigned length = data.length();
@@ -989,8 +987,6 @@ String TextControlElement::ValueWithHardLineBreaks() const {
   for (Node& node : NodeTraversal::DescendantsOf(*inner_text)) {
     if (IsA<HTMLBRElement>(node)) {
       DCHECK_EQ(&node, inner_text->lastChild());
-      if (&node != inner_text->lastChild())
-        result.Append(kNewlineCharacter);
     } else if (auto* text_node = DynamicTo<Text>(node)) {
       String data = text_node->data();
       unsigned length = data.length();