Do not break after ZWJ if the trailing character is Emoji.

third_party/WebKit/Source/core/editing/EditingUtilitiesTest.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/editing/EditingUtilities.h"
 
 #include "core/dom/StaticNodeList.h"
 #include "core/editing/EditingTestBase.h"
 
 namespace blink {
@@ skipping 532 matching lines @@
     EXPECT_EQ(0, previousGraphemeBoundaryOf(node, 3));
     EXPECT_EQ(3, nextGraphemeBoundaryOf(node, 0));
     EXPECT_EQ(4, nextGraphemeBoundaryOf(node, 3));
     setBodyContent("<p id='target'>a&#x200D;&#x1F466;b</p>"); // ZWJ x EBG
     node = document().getElementById("target")->firstChild();
     EXPECT_EQ(4, previousGraphemeBoundaryOf(node, 5));
     EXPECT_EQ(0, previousGraphemeBoundaryOf(node, 4));
     EXPECT_EQ(4, nextGraphemeBoundaryOf(node, 0));
     EXPECT_EQ(5, nextGraphemeBoundaryOf(node, 4));
 
+    // Not only Glue_After_ZWJ or EBG but also other emoji shouldn't break
+    // before ZWJ.
+    // U+1F5FA(WORLD MAP) doesn't have either Glue_After_Zwj or EBG but has
+    // Emoji property.
+    setBodyContent("<p id='target'>&#x200D;&#x1F5FA;</p>");
+    node = document().getElementById("target")->firstChild();
+    EXPECT_EQ(0, previousGraphemeBoundaryOf(node, 3));
+    EXPECT_EQ(3, nextGraphemeBoundaryOf(node, 0));
+
     // GB999: Otherwise break everywhere.
     // Breaks between Hangul syllable except for GB6, GB7, GB8.
     setBodyContent("<p id='target'>" + L + T + "</p>");
     node = document().getElementById("target")->firstChild();
     EXPECT_EQ(1, previousGraphemeBoundaryOf(node, 2));
     EXPECT_EQ(1, nextGraphemeBoundaryOf(node, 0));
     setBodyContent("<p id='target'>" + V + L + "</p>");
     node = document().getElementById("target")->firstChild();
     EXPECT_EQ(1, previousGraphemeBoundaryOf(node, 2));
     EXPECT_EQ(1, nextGraphemeBoundaryOf(node, 0));
@@ skipping 56 matching lines @@
     EXPECT_EQ(1, previousGraphemeBoundaryOf(node, 3));
     EXPECT_EQ(1, nextGraphemeBoundaryOf(node, 0));
     // U+1F5FA(WORLD MAP) doesn't have either E_Base or EBG property.
     setBodyContent("<p id='target'>&#x1F5FA;&#x1F3FB;</p>");
     node = document().getElementById("target")->firstChild();
     EXPECT_EQ(2, previousGraphemeBoundaryOf(node, 4));
     EXPECT_EQ(2, nextGraphemeBoundaryOf(node, 0));
 
     // For GB11, if trailing character is not Glue_After_Zwj or EBG, break happens after ZWJ.
     // U+1F5FA(WORLD MAP) doesn't have either Glue_After_Zwj or EBG.
-    setBodyContent("<p id='target'>&#x200D;&#x1F5FA;</p>");
+    setBodyContent("<p id='target'>&#x200D;a</p>");
     node = document().getElementById("target")->firstChild();
-    EXPECT_EQ(1, previousGraphemeBoundaryOf(node, 3));
+    EXPECT_EQ(1, previousGraphemeBoundaryOf(node, 2));
     EXPECT_EQ(1, nextGraphemeBoundaryOf(node, 0));
 }
 
 TEST_F(EditingUtilitiesTest, previousPositionOf_Backspace)
 {
     // BMP characters. Only one code point should be deleted.
     setBodyContent("<p id='target'>abc</p>");
     Node* node = document().getElementById("target")->firstChild();
     EXPECT_EQ(Position(node, 2), previousPositionOf(Position(node, 3), PositionMoveType::BackwardDeletion));
     EXPECT_EQ(Position(node, 1), previousPositionOf(Position(node, 2), PositionMoveType::BackwardDeletion));
@@ skipping 82 matching lines @@
 
     // Edge case: specify middle of surrogate pairs.
     setBodyContent("<p id='target'>&#x1F441;&#x1F441;&#x1F441</p>");
     node = document().getElementById("target")->firstChild();
     EXPECT_EQ(Position(node, 4), previousPositionOf(Position(node, 5), PositionMoveType::BackwardDeletion));
     EXPECT_EQ(Position(node, 2), previousPositionOf(Position(node, 3), PositionMoveType::BackwardDeletion));
     EXPECT_EQ(Position(node, 0), previousPositionOf(Position(node, 1), PositionMoveType::BackwardDeletion));
 }
 
 } // namespace blink