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

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

Index: third_party/WebKit/Source/core/dom/Text.cpp
diff --git a/third_party/WebKit/Source/core/dom/Text.cpp b/third_party/WebKit/Source/core/dom/Text.cpp
index a105811975803ddc44edf75f845d6386a3f5d22c..325cfb89ccaee816c99dae94a775edcd4f68b27c 100644
--- a/third_party/WebKit/Source/core/dom/Text.cpp
+++ b/third_party/WebKit/Source/core/dom/Text.cpp
@@ -82,12 +82,12 @@ Node* Text::mergeNextSiblingNodesIfPossible() {
     setDataWithoutUpdate(data() + nextTextData);
     updateTextLayoutObject(oldTextData.length(), 0);
 
+    document().didMergeTextNodes(*this, *nextText, offset);
+
     // Empty nextText for layout update.
     nextText->setDataWithoutUpdate(emptyString());
     nextText->updateTextLayoutObject(0, nextTextData.length());
 
-    document().didMergeTextNodes(*nextText, offset);
-
     // Restore nextText for mutation event.
     nextText->setDataWithoutUpdate(nextTextData);
     nextText->updateTextLayoutObject(0, 0);