[LayoutNG] Implement LayoutText::AbsoluteRects

Another round to port InlineTextBox code to LayoutNG.

This function is used by Slider and testing/internals.

Bug: 636993
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Iac2bbb59f49b02aeb0fd2e95cda5477a9160c444
Reviewed-on: https://chromium-review.googlesource.com/981574Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546244}

third_party/WebKit/Source/core/layout/LayoutText.cpp

@@ -325,6 +325,31 @@ String LayoutText::PlainText() const {
 
 void LayoutText::AbsoluteRects(Vector<IntRect>& rects,
                                const LayoutPoint& accumulated_offset) const {
+  if (RuntimeEnabledFeatures::LayoutNGEnabled()) {
+    auto fragments = NGPaintFragment::InlineFragmentsFor(this);
+    if (fragments.IsInLayoutNGInlineFormattingContext()) {
+      Vector<LayoutRect, 32> layout_rects;
+      for (const NGPaintFragment* fragment : fragments) {
+        layout_rects.push_back(
+            LayoutRect(fragment->InlineOffsetToContainerBox().ToLayoutPoint(),
+                       fragment->Size().ToLayoutSize()));
+      }
+      // |rect| is in flipped block physical coordinate, but LayoutNG is in
+      // physical coordinate. Flip if needed.
+      if (UNLIKELY(HasFlippedBlocksWritingMode())) {
+        LayoutBlock* block = ContainingBlock();
+        DCHECK(block);
+        for (LayoutRect& rect : layout_rects)
+          block->FlipForWritingMode(rect);
+      }
+      for (LayoutRect& rect : layout_rects) {
+        rect.MoveBy(accumulated_offset);
+        rects.push_back(EnclosingIntRect(rect));
+      }
+      return;
+    }
+  }
+
   for (InlineTextBox* box : TextBoxes()) {
     rects.push_back(EnclosingIntRect(LayoutRect(
         LayoutPoint(accumulated_offset) + box->Location(), box->Size())));

third_party/WebKit/Source/core/layout/LayoutTextTest.cpp

@@ -8,6 +8,7 @@
 #include "core/testing/CoreUnitTestHelper.h"
 #include "platform/runtime_enabled_features.h"
 #include "platform/testing/runtime_enabled_features_test_helpers.h"
+#include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
@@ -428,6 +429,44 @@ TEST_P(ParameterizedLayoutTextTest, GetUpperLeftCornerVLR) {
   EXPECT_EQ(FloatPoint(10, 30), upper_left.value());
 }
 
+TEST_P(ParameterizedLayoutTextTest, AbsoluteRects) {
+  LoadAhem();
+  SetBodyInnerHTML(R"HTML(
+    <style>
+    div {
+      font: 10px/1 Ahem;
+      width: 5em;
+    }
+    </style>
+    <div>012<span id=target>345 67</span></div>
+  )HTML");
+  LayoutText* layout_text = GetLayoutTextById("target");
+  Vector<IntRect> rects;
+  layout_text->AbsoluteRects(rects, {LayoutUnit(100), LayoutUnit(200)});
+  EXPECT_THAT(rects, testing::ElementsAre(IntRect(130, 200, 30, 10),
+                                          IntRect(100, 210, 20, 10)));
+}
+
+TEST_P(ParameterizedLayoutTextTest, AbsoluteRectsVRL) {
+  LoadAhem();
+  SetBodyInnerHTML(R"HTML(
+    <style>
+    div {
+      font: 10px/1 Ahem;
+      width: 10em;
+      height: 5em;
+      writing-mode: vertical-rl;
+    }
+    </style>
+    <div>012<span id=target>345 67</span></div>
+  )HTML");
+  LayoutText* layout_text = GetLayoutTextById("target");
+  Vector<IntRect> rects;
+  layout_text->AbsoluteRects(rects, {LayoutUnit(100), LayoutUnit(200)});
+  EXPECT_THAT(rects, testing::ElementsAre(IntRect(100, 230, 10, 30),
+                                          IntRect(110, 200, 10, 20)));
+}
+
 TEST_P(ParameterizedLayoutTextTest, LinesBoundingBox) {
   LoadAhem();
   SetBasicBody(