Make NGInlineNode::ShapeText() not to reuse ShapeResult for letter-spacing

This patch changes |NGInlineNode::ShapeText()| not to reuse
|ShapeResult| for text with CSS property "letter-spacing" because we
modify |ShapeResult| directly to apply letter spacing. Thus, letter-
spacing is applied more than once on reused portion of |ShapeResult|.

Note: This patch also changes number of bits of
|SharepResult::num_glyphs_| from 30 to 29 to hold bit flags in
|unsigned| (32-bit) for re-landing[1].

[1] http://crrev.com/c/2390615 Revert "Make NGInlineNode::ShapeText()
not to reuse ShapeResult for letter-spacing"

Bug: 1124446
Change-Id: I120cc379a191e1499ac1548a569474ed03d0f6a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391890
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804185}

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

@@ -231,6 +231,8 @@ class ReusingTextShaper final {
         continue;
       if (!item->TextShapeResult() || item->Direction() != direction)
         continue;
+      if (item->TextShapeResult()->IsAppliedSpacing())
+        continue;
       shape_results.push_back(item->TextShapeResult());
     }
     return shape_results;

third_party/blink/renderer/platform/fonts/shaping/shape_result.cc

@@ -63,6 +63,20 @@ struct SameSizeAsHarfBuzzRunGlyphData {
 
 ASSERT_SIZE(HarfBuzzRunGlyphData, SameSizeAsHarfBuzzRunGlyphData);
 
+struct SameSizeAsShapeResult : RefCounted<SameSizeAsShapeResult> {
+  float width_;
+  FloatRect deprecated_ink_bounds_;
+  Vector<scoped_refptr<ShapeResult::RunInfo>> runs_;
+  scoped_refptr<const SimpleFontData> primary_font_;
+  std::unique_ptr<int> character_position_;
+
+  unsigned start_index_;
+  unsigned num_characters_;
+  unsigned flags;
+};
+
+ASSERT_SIZE(ShapeResult, SameSizeAsShapeResult);
+
 unsigned ShapeResult::RunInfo::NextSafeToBreakOffset(unsigned offset) const {
   DCHECK_LE(offset, num_characters_);
   if (!Rtl()) {
@@ -370,7 +384,8 @@ ShapeResult::ShapeResult(scoped_refptr<const SimpleFontData> font_data,
       num_characters_(num_characters),
       num_glyphs_(0),
       direction_(static_cast<unsigned>(direction)),
-      has_vertical_offsets_(0) {}
+      has_vertical_offsets_(false),
+      is_applied_spacing_(false) {}
 
 ShapeResult::ShapeResult(const Font* font,
                          unsigned start_index,
@@ -892,6 +907,7 @@ void ShapeResult::ApplySpacingImpl(
 
 void ShapeResult::ApplySpacing(ShapeResultSpacing<String>& spacing,
                                int text_start_offset) {
+  is_applied_spacing_ = true;
   ApplySpacingImpl(spacing, text_start_offset);
 }
 

third_party/blink/renderer/platform/fonts/shaping/shape_result.h

@@ -185,6 +185,9 @@ class PLATFORM_EXPORT ShapeResult : public RefCounted<ShapeResult> {
   // have vertical offsets.
   bool HasVerticalOffsets() const { return has_vertical_offsets_; }
 
+  // Note: We should not reuse |ShapeResult| if we call |ApplySpacing()|.
+  bool IsAppliedSpacing() const { return is_applied_spacing_; }
+
   // For memory reporting.
   size_t ByteSize() const;
 
@@ -490,7 +493,7 @@ class PLATFORM_EXPORT ShapeResult : public RefCounted<ShapeResult> {
 
   unsigned start_index_;
   unsigned num_characters_;
-  unsigned num_glyphs_ : 30;
+  unsigned num_glyphs_ : 29;
 
   // Overall direction for the TextRun, dictates which order each individual
   // sub run (represented by RunInfo structs in the m_runs vector) can have a
@@ -500,6 +503,12 @@ class PLATFORM_EXPORT ShapeResult : public RefCounted<ShapeResult> {
   // Tracks whether any runs contain glyphs with a y-offset != 0.
   unsigned has_vertical_offsets_ : 1;
 
+  // True once called |ApplySpacing()|.
+  unsigned is_applied_spacing_ : 1;
+
+  // Note: When you add more bit flags, please consider to reduce size of
+  // |num_glyphs_| or |num_characters_|.
+
  private:
   friend class HarfBuzzShaper;
   friend class ShapeResultBuffer;

third_party/blink/web_tests/editing/inserting/typing_letter_spacing-expected.html

+<!doctype html>
+<script src="../../resources/ahem.js"></script>
+<style>
+#target {
+    font: 10px/15px Ahem;
+    letter-spacing: 20px;
+}
+</style>
+<div id="target">abcx</div>

third_party/blink/web_tests/editing/inserting/typing_letter_spacing.html

+<!doctype html>
+<script src="../../resources/ahem.js"></script>
+<style>
+#target {
+    font: 10px/15px Ahem;
+    letter-spacing: 20px;
+}
+</style>
+<div id="target">x</div>
+<script>
+const text = target.firstChild;
+function typing(character) {
+    text.replaceData(0, 0, character);
+    document.body.offsetHeight;
+}
+typing('a');
+typing('b');
+typing('c');
+</script>