Make SynchronousMutationObserver::didMergeTextNodes() to take both merged and merging nodes

third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp

Index: third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp
diff --git a/third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp b/third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp
index 3d2f24897845ec2a53ddb6a01c70aff05636cb24..506cdb9409007cfba208fc809df03de25a270a0d 100644
--- a/third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp
+++ b/third_party/WebKit/Source/core/dom/SynchronousMutationNotifier.cpp
@@ -17,10 +17,12 @@ void SynchronousMutationNotifier::notifyChangeChildren(
     observer->didChangeChildren(container);
 }
 
-void SynchronousMutationNotifier::notifyMergeTextNodes(Text& node,
-                                                       unsigned offset) {
+void SynchronousMutationNotifier::notifyMergeTextNodes(
+    const Text& node,
+    const NodeWithIndex& nodeToBeRemovedWithIndex,
+    unsigned oldLength) {
   for (SynchronousMutationObserver* observer : m_observers)
-    observer->didMergeTextNodes(node, offset);
+    observer->didMergeTextNodes(node, nodeToBeRemovedWithIndex, oldLength);
 }
 
 void SynchronousMutationNotifier::notifyMoveTreeToNewDocument(