Don't merge adjacent composition markers.

Source/core/editing/markers/DocumentMarkerController.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 196 matching lines @@
     if (!markers->at(markerListIndex)) {
         markers->insert(markerListIndex, adoptPtrWillBeNoop(new MarkerList));
     }
 
     OwnPtrWillBeMember<MarkerList>& list = markers->at(markerListIndex);
     OwnPtrWillBeRawPtr<RenderedDocumentMarker> newRenderedMarker = RenderedDocumentMarker::create(newMarker);
     updateMarkerRenderedRect(node, *newRenderedMarker);
     if (list->isEmpty() || list->last()->endOffset() < newMarker.startOffset()) {
         list->append(newRenderedMarker.release());
     } else {
-        if (newMarker.type() != DocumentMarker::TextMatch) {
+        if (newMarker.type() != DocumentMarker::TextMatch && newMarker.type() != DocumentMarker::Composition) {
             mergeOverlapping(list.get(), newRenderedMarker.release());
         } else {
             MarkerList::iterator pos = std::lower_bound(list->begin(), list->end(), &newMarker, startsFurther);
             list->insert(pos - list->begin(), newRenderedMarker.release());
         }
     }
 
     // repaint the affected node
     if (node->layoutObject())
         node->layoutObject()->setShouldDoFullPaintInvalidation();
@@ skipping 514 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 void showDocumentMarkers(const blink::DocumentMarkerController* controller)
 {
     if (controller)
         controller->showMarkers();
 }
 #endif