[LayoutNG] Remove trailing spaces of blocks in phase 1

This patch changes NGInlineItemsBuilder to remove trailing
spaces at the end of blocks.

It used to do so, but stopped in https://crrev.com/c/1022191
because doing so reduces opportunities to re-use NGInlineItem
and increases shaping when contents are added.

However, for fonts that has kerning before a space character,
this change increased re-shaping every block end. Given line
breaking is more often ran than adding contents dynamically,
this turned out to be not a good trade off. We could re-shape
only end-part in RestoreTrailingCollapsibleSpace to achieve
the originally intended optimizations.

This speeds up blink_perf tests on Windows by ~10%.

This patch also fixes a few cases where space collapsing is
incorrect when items are re-used.

Bug: 636993
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Id6e0c262db29b4d39ddd4eb1f55b18da2c7e5880
Reviewed-on: https://chromium-review.googlesource.com/1163240
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581149}

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/css2.1/20110323/list-style-position-005-expected.txt

@@ -13,9 +13,9 @@ layer at (0,0) size 800x262
           text run at (124,0) width 274: " be a green bar stacked on top of a blue bar."
       LayoutNGListItem {DIV} at (0,36) size 784x202 [color=#00FF00] [bgcolor=#00FF00]
         LayoutNGBlockFlow (anonymous) at (0,0) size 784x101
-          LayoutInline (anonymous) at (0,0) size 30x97
-            LayoutText (anonymous) at (-1,2) size 30x97
-              text run at (-1,2) width 30: "\x{2022}"
+          LayoutInline (anonymous) at (0,0) size 27x97
+            LayoutText (anonymous) at (-1,2) size 27x97
+              text run at (-1,2) width 27: "\x{2022}"
         LayoutNGBlockFlow {DIV} at (0,101) size 784x101 [bgcolor=#0000FF]
           LayoutText {#text} at (0,2) size 21x97
             text run at (0,2) width 21: " "

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/css2.1/t1202-counter-13-b-expected.txt

@@ -73,10 +73,10 @@ layer at (0,0) size 800x100
               text run at (139,0) width 12: "K"
         LayoutText {#text} at (151,0) size 4x19
           text run at (151,0) width 4: " "
-        LayoutInline {SPAN} at (0,0) size 9x19
-          LayoutInline {<pseudo:before>} at (0,0) size 9x19
-            LayoutCounter (anonymous) at (155,0) size 9x19
-              text run at (155,0) width 9: "L"
+        LayoutInline {SPAN} at (0,0) size 10x19
+          LayoutInline {<pseudo:before>} at (0,0) size 10x19
+            LayoutCounter (anonymous) at (155,0) size 10x19
+              text run at (155,0) width 10: "L"
         LayoutText {#text} at (0,0) size 0x0
       LayoutNGBlockFlow {DIV} at (0,56) size 784x20
         LayoutText {#text} at (0,0) size 165x19

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/css2.1/t1202-counter-14-b-expected.txt

@@ -73,10 +73,10 @@ layer at (0,0) size 800x100
               text run at (139,0) width 12: "K"
         LayoutText {#text} at (151,0) size 4x19
           text run at (151,0) width 4: " "
-        LayoutInline {SPAN} at (0,0) size 9x19
-          LayoutInline {<pseudo:before>} at (0,0) size 9x19
-            LayoutCounter (anonymous) at (155,0) size 9x19
-              text run at (155,0) width 9: "L"
+        LayoutInline {SPAN} at (0,0) size 10x19
+          LayoutInline {<pseudo:before>} at (0,0) size 10x19
+            LayoutCounter (anonymous) at (155,0) size 10x19
+              text run at (155,0) width 10: "L"
         LayoutText {#text} at (0,0) size 0x0
       LayoutNGBlockFlow {DIV} at (0,56) size 784x20
         LayoutText {#text} at (0,0) size 165x19

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/css2.1/t1202-counters-13-b-expected.txt

@@ -73,10 +73,10 @@ layer at (0,0) size 800x100
               text run at (289,0) width 28: "A.K"
         LayoutText {#text} at (317,0) size 3x19
           text run at (317,0) width 3: " "
-        LayoutInline {SPAN} at (0,0) size 25x19
-          LayoutInline {<pseudo:before>} at (0,0) size 25x19
-            LayoutCounter (anonymous) at (320,0) size 25x19
-              text run at (320,0) width 25: "A.L"
+        LayoutInline {SPAN} at (0,0) size 26x19
+          LayoutInline {<pseudo:before>} at (0,0) size 26x19
+            LayoutCounter (anonymous) at (320,0) size 26x19
+              text run at (320,0) width 26: "A.L"
         LayoutText {#text} at (0,0) size 0x0
       LayoutNGBlockFlow {DIV} at (0,56) size 784x20
         LayoutText {#text} at (0,0) size 346x19

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/css2.1/t1202-counters-14-b-expected.txt

@@ -73,10 +73,10 @@ layer at (0,0) size 800x100
               text run at (289,0) width 28: "A.K"
         LayoutText {#text} at (317,0) size 3x19
           text run at (317,0) width 3: " "
-        LayoutInline {SPAN} at (0,0) size 25x19
-          LayoutInline {<pseudo:before>} at (0,0) size 25x19
-            LayoutCounter (anonymous) at (320,0) size 25x19
-              text run at (320,0) width 25: "A.L"
+        LayoutInline {SPAN} at (0,0) size 26x19
+          LayoutInline {<pseudo:before>} at (0,0) size 26x19
+            LayoutCounter (anonymous) at (320,0) size 26x19
+              text run at (320,0) width 26: "A.L"
         LayoutText {#text} at (0,0) size 0x0
       LayoutNGBlockFlow {DIV} at (0,56) size 784x20
         LayoutText {#text} at (0,0) size 346x19

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/fast/events/mouseclick-target-and-positioning-expected.txt

 This page tests whether a click event propagates with the correct target and positioning. See rdar://problem/4477126.
 
 click inside the red box:[]
+PASS: event target should be [object HTMLSpanElement] and is
+PASS: event.pageX should be 175 and is
+PASS: event.pageY should be 105 and is
+PASS: event.clientX should be 175 and is
+PASS: event.clientY should be 105 and is
+PASS: event.layerX should be 7 and is
+PASS: event.layerY should be 5 and is
+PASS: event.offsetX should be 7 and is
+PASS: event.offsetY should be 5 and is
+PASS: event.x should be 175 and is
+PASS: event.y should be 105 and is

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/images/imagemap-focus-ring-in-positioned-container-expected.txt

+layer at (0,0) size 800x600
+  LayoutView at (0,0) size 800x600
+layer at (0,0) size 800x36
+  LayoutNGBlockFlow {HTML} at (0,0) size 800x36
+    LayoutNGBlockFlow {BODY} at (8,8) size 784x20
+      LayoutText {#text} at (0,0) size 551x19
+        text run at (0,0) width 551: "Tests that we paint area outline properly when the image is inside positioned containers."
+layer at (20,50) size 0x0
+  LayoutNGBlockFlow (positioned) {DIV} at (20,50) size 0x0
+layer at (30,60) size 50x55
+  LayoutNGBlockFlow (positioned) {DIV} at (10,10) size 50x55
+    LayoutImage {IMG} at (0,0) size 50x50
+    LayoutText {#text} at (0,0) size 0x0
+    LayoutInline {MAP} at (0,0) size 0x19
+      LayoutInline {AREA} at (0,0) size 0x19
+    LayoutText {#text} at (0,0) size 0x0

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/images/imagemap-focus-ring-with-paint-root-offset-expected.txt

+layer at (0,0) size 800x600
+  LayoutView at (0,0) size 800x600
+layer at (0,0) size 800x36
+  LayoutNGBlockFlow {HTML} at (0,0) size 800x36
+    LayoutNGBlockFlow {BODY} at (8,8) size 784x20
+      LayoutText {#text} at (0,0) size 437x19
+        text run at (0,0) width 437: "Tests that we paint area outline properly when the paintroot is shifted."
+layer at (5,50) size 50x55
+  LayoutNGBlockFlow (positioned) {DIV} at (5,50) size 50x55
+    LayoutImage {IMG} at (0,0) size 50x50
+    LayoutText {#text} at (0,0) size 0x0
+    LayoutInline {MAP} at (0,0) size 0x19
+      LayoutInline {AREA} at (0,0) size 0x19
+    LayoutText {#text} at (0,0) size 0x0

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/virtual/gpu-rasterization/images/imagemap-focus-ring-in-positioned-container-expected.txt

+layer at (0,0) size 800x600
+  LayoutView at (0,0) size 800x600
+layer at (0,0) size 800x36
+  LayoutNGBlockFlow {HTML} at (0,0) size 800x36
+    LayoutNGBlockFlow {BODY} at (8,8) size 784x20
+      LayoutText {#text} at (0,0) size 551x19
+        text run at (0,0) width 551: "Tests that we paint area outline properly when the image is inside positioned containers."
+layer at (20,50) size 0x0
+  LayoutNGBlockFlow (positioned) {DIV} at (20,50) size 0x0
+layer at (30,60) size 50x55
+  LayoutNGBlockFlow (positioned) {DIV} at (10,10) size 50x55
+    LayoutImage {IMG} at (0,0) size 50x50
+    LayoutText {#text} at (0,0) size 0x0
+    LayoutInline {MAP} at (0,0) size 0x19
+      LayoutInline {AREA} at (0,0) size 0x19
+    LayoutText {#text} at (0,0) size 0x0

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/virtual/gpu-rasterization/images/imagemap-focus-ring-with-paint-root-offset-expected.txt

+layer at (0,0) size 800x600
+  LayoutView at (0,0) size 800x600
+layer at (0,0) size 800x36
+  LayoutNGBlockFlow {HTML} at (0,0) size 800x36
+    LayoutNGBlockFlow {BODY} at (8,8) size 784x20
+      LayoutText {#text} at (0,0) size 437x19
+        text run at (0,0) width 437: "Tests that we paint area outline properly when the paintroot is shifted."
+layer at (5,50) size 50x55
+  LayoutNGBlockFlow (positioned) {DIV} at (5,50) size 50x55
+    LayoutImage {IMG} at (0,0) size 50x50
+    LayoutText {#text} at (0,0) size 0x0
+    LayoutInline {MAP} at (0,0) size 0x19
+      LayoutInline {AREA} at (0,0) size 0x19
+    LayoutText {#text} at (0,0) size 0x0

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

@@ -56,8 +56,7 @@ NGInlineItem::NGInlineItem(NGInlineItemType type,
                            unsigned start,
                            unsigned end,
                            const ComputedStyle* style,
-                           LayoutObject* layout_object,
-                           bool end_may_collapse)
+                           LayoutObject* layout_object)
     : start_offset_(start),
       end_offset_(end),
       style_(style),
@@ -72,7 +71,7 @@ NGInlineItem::NGInlineItem(NGInlineItemType type,
       should_create_box_fragment_(false),
       style_variant_(static_cast<unsigned>(NGStyleVariant::kStandard)),
       end_collapse_type_(kNotCollapsible),
-      end_may_collapse_(end_may_collapse),
+      is_end_collapsible_newline_(false),
       is_symbol_marker_(false) {
   DCHECK_GE(end, start);
   ComputeBoxProperties();
@@ -97,7 +96,7 @@ NGInlineItem::NGInlineItem(const NGInlineItem& other,
       should_create_box_fragment_(other.should_create_box_fragment_),
       style_variant_(other.style_variant_),
       end_collapse_type_(other.end_collapse_type_),
-      end_may_collapse_(other.end_may_collapse_),
+      is_end_collapsible_newline_(other.is_end_collapsible_newline_),
       is_symbol_marker_(other.is_symbol_marker_) {
   DCHECK_GE(end, start);
 }
@@ -329,4 +328,15 @@ bool NGInlineItem::HasEndEdge() const {
          !ToLayoutInline(GetLayoutObject())->Continuation();
 }
 
+void NGInlineItem::SetEndCollapseType(NGCollapseType type) {
+  DCHECK(Type() == NGInlineItem::kText || type == kOpaqueToCollapsing ||
+         (Type() == NGInlineItem::kControl && type == kCollapsible));
+  end_collapse_type_ = type;
+}
+
+void NGInlineItem::SetEndCollapseType(NGCollapseType type, bool is_newline) {
+  SetEndCollapseType(type);
+  is_end_collapsible_newline_ = is_newline;
+}
+
 }  // namespace blink

third_party/blink/renderer/core/layout/ng/inline/ng_inline_item.h

@@ -51,12 +51,12 @@ class CORE_EXPORT NGInlineItem {
   enum NGCollapseType {
     // No collapsible spaces.
     kNotCollapsible,
-    // A collapsible space run that does not contain segment breaks.
-    kCollapsibleSpace,
-    // A collapsible space run that contains segment breaks.
-    kCollapsibleNewline,
     // This item is opaque to whitespace collapsing.
-    kOpaqueToCollapsing
+    kOpaqueToCollapsing,
+    // This item ends with collapsible spaces.
+    kCollapsible,
+    // Collapsible spaces at the end of this item were collapsed.
+    kCollapsed,
   };
 
   // The constructor and destructor can't be implicit or inlined, because they
@@ -65,8 +65,7 @@ class CORE_EXPORT NGInlineItem {
                unsigned start,
                unsigned end,
                const ComputedStyle* style = nullptr,
-               LayoutObject* layout_object = nullptr,
-               bool end_may_collapse = false);
+               LayoutObject* layout_object = nullptr);
   ~NGInlineItem();
 
   // Copy constructor adjusting start/end and shape results.
@@ -123,12 +122,12 @@ class CORE_EXPORT NGInlineItem {
   NGCollapseType EndCollapseType() const {
     return static_cast<NGCollapseType>(end_collapse_type_);
   }
-  void SetEndCollapseType(NGCollapseType type) { end_collapse_type_ = type; }
+  void SetEndCollapseType(NGCollapseType type);
 
-  // Whether the item may be affected by whitespace collapsing. Unlike the
-  // EndCollapseType() method this returns true even if a trailing space has
-  // been removed.
-  bool EndMayCollapse() const { return end_may_collapse_; }
+  // Whether the end collapsible space run contains a newline.
+  // Valid only when kCollapsible or kCollapsed.
+  bool IsEndCollapsibleNewline() const { return is_end_collapsible_newline_; }
+  void SetEndCollapseType(NGCollapseType type, bool is_newline);
 
   static void Split(Vector<NGInlineItem>&, unsigned index, unsigned offset);
 
@@ -189,7 +188,7 @@ class CORE_EXPORT NGInlineItem {
   unsigned should_create_box_fragment_ : 1;
   unsigned style_variant_ : 2;
   unsigned end_collapse_type_ : 2;  // NGCollapseType
-  unsigned end_may_collapse_ : 1;
+  unsigned is_end_collapsible_newline_ : 1;
   unsigned is_symbol_marker_ : 1;
   friend class NGInlineNode;
 };

third_party/blink/renderer/core/layout/ng/inline/ng_inline_items_builder.h

@@ -154,13 +154,12 @@ class NGInlineItemsBuilderTemplate {
   void RemoveTrailingCollapsibleSpaceIfExists();
   void RemoveTrailingCollapsibleSpace(NGInlineItem*);
 
+  void RestoreTrailingCollapsibleSpaceIfRemoved();
+  void RestoreTrailingCollapsibleSpace(NGInlineItem*);
+
   void Exit(LayoutObject*);
 };
 
-template <>
-CORE_EXPORT String
-NGInlineItemsBuilderTemplate<NGOffsetMappingBuilder>::ToString();
-
 template <>
 CORE_EXPORT bool NGInlineItemsBuilderTemplate<NGOffsetMappingBuilder>::Append(
     const String&,

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

@@ -294,16 +294,12 @@ const NGOffsetMapping* NGInlineNode::ComputeOffsetMappingIfNeeded() {
     NGInlineItemsBuilderForOffsetMapping builder(&items);
     CollectInlinesInternal(GetLayoutBlockFlow(), &builder, nullptr);
     String text = builder.ToString();
-
-    // The trailing space of the text for offset mapping may be removed. If not,
-    // share the string instance.
-    if (text == data->text_content)
-      text = data->text_content;
+    DCHECK_EQ(data->text_content, text);
 
     // TODO(xiaochengh): This doesn't compute offset mapping correctly when
     // text-transform CSS property changes text length.
     NGOffsetMappingBuilder& mapping_builder = builder.GetOffsetMappingBuilder();
-    mapping_builder.SetDestinationString(text);
+    mapping_builder.SetDestinationString(data->text_content);
     data->offset_mapping =
         std::make_unique<NGOffsetMapping>(mapping_builder.Build());
   }