[LayoutNG] Make LayoutText to associate to proper NGInlineItem objects

This patch changes |NGInlineNode::AssociateItemsWithInlines()| to associate
|NGInlineItem| to |LayoutText| correctly by skipping |NGInlineItem| without
layout object.

Before this patch, |LayoutText| is assocaited |NGIninlineItem| objects
after the |NGIninlineItem.layout_object == nullptr|.

This patch is a preparation of the patch[1].

[1] http://crrev.com/c/1309562 Make Element#innterText to utilize NGInlineItem
instead of NGPaintFragment

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I41f16ea13ca1e0641cb2a42331d64fa2cd6387ac
Reviewed-on: https://chromium-review.googlesource.com/c/1317217
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605592}

third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.cc

@@ -639,7 +639,9 @@ void NGInlineNode::AssociateItemsWithInlines(NGInlineNodeData* data) {
   LayoutObject* last_object = nullptr;
   for (auto& item : data->items) {
     LayoutObject* object = item.GetLayoutObject();
-    if (object && object->IsText()) {
+    if (!object)
+      continue;
+    if (object->IsText()) {
       LayoutText* layout_text = ToLayoutText(object);
       if (object != last_object)
         layout_text->ClearInlineItems();

third_party/blink/renderer/core/layout/ng/inline/ng_inline_node_test.cc

@@ -490,6 +490,19 @@ TEST_F(NGInlineNodeTest, MinMaxSizeFloatsClearance) {
   EXPECT_EQ(160, sizes.max_size);
 }
 
+TEST_F(NGInlineNodeTest, AssociatedItemsWithControlItem) {
+  SetBodyInnerHTML(
+      "<pre id=t style='-webkit-rtl-ordering:visual'>ab\nde</pre>");
+  LayoutText* const layout_text = ToLayoutText(
+      GetDocument().getElementById("t")->firstChild()->GetLayoutObject());
+  ASSERT_TRUE(layout_text->HasValidInlineItems());
+  const Vector<NGInlineItem*>& items = layout_text->InlineItems();
+  ASSERT_EQ(3u, items.size());
+  TEST_ITEM_TYPE_OFFSET((*items[0]), kText, 1u, 3u);
+  TEST_ITEM_TYPE_OFFSET((*items[1]), kControl, 4u, 5u);
+  TEST_ITEM_TYPE_OFFSET((*items[2]), kText, 6u, 8u);
+}
+
 TEST_F(NGInlineNodeTest, InvalidateAddSpan) {
   SetupHtml("t", "<div id=t>before</div>");
   EXPECT_FALSE(layout_block_flow_->NeedsCollectInlines());