[All-In-One] Introduce BackspaceStateMachine

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

Index: third_party/WebKit/Source/core/editing/EditingUtilities.cpp
diff --git a/third_party/WebKit/Source/core/editing/EditingUtilities.cpp b/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
index a5748f859505025388e33c7a977601d7afb6f13f..8dc5caad2478089dc78a23645216774a8ab0bf10 100644
--- a/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
+++ b/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
@@ -32,6 +32,7 @@
 #include "core/dom/Range.h"
 #include "core/dom/Text.h"
 #include "core/dom/shadow/ShadowRoot.h"
+#include "core/editing/BackspaceStateMachine.h"
 #include "core/editing/EditingStrategy.h"
 #include "core/editing/Editor.h"
 #include "core/editing/PlainTextRange.h"
@@ -556,9 +557,25 @@ int uncheckedPreviousOffset(const Node* node, int current)
     return result == TextBreakDone ? current - 1 : result;
 }
 
-static int uncheckedPreviousOffsetForBackwardDeletion(const Node* n, int current)
+static int uncheckedPreviousOffsetForBackwardDeletion(const Node* node, int current)
 {
-    return n->layoutObject() ? n->layoutObject()->previousOffsetForBackwardDeletion(current) : current - 1;
+    DCHECK_GE(current, 0);
+    if (current <= 1)
+        return 0;
+    if (!node->isTextNode())
+        return current - 1;
+
+    const String& text = toText(node)->data();
+    CHECK(static_cast<unsigned>(current - 1) < text.length());
+    BackspaceStateMachine machine;
+    for (int i = current - 1; i >= 0; --i) {
+        if (machine.updateState(text[i]))
+            break;
+    }
+    const int amount = machine.finalizeAndGetCodeUnitCountToBeDeleted();
+    DCHECK_GE(amount, 1);
+    DCHECK_GE(current, amount);
+    return current - amount;
 }
 
 int uncheckedNextOffset(const Node* node, int current)