Don't merge adjacent composition markers.

Source/core/editing/markers/DocumentMarkerControllerTest.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 227 matching lines @@
     EXPECT_EQ(1u, renderedRects.size());
     EXPECT_NE(invalidRect, renderedRects[0]);
 
     div->setAttribute(HTMLNames::styleAttr, "margin: 200px");
     document().updateLayout();
     Vector<IntRect> newRenderedRects = markerController().renderedRectsForMarkers(DocumentMarker::Composition);
     EXPECT_EQ(1u, newRenderedRects.size());
     EXPECT_NE(renderedRects[0], newRenderedRects[0]);
 }
 
+TEST_F(DocumentMarkerControllerTest, CompositionMarkersNotMerged)
+{
+    IntRect invalidRect(RenderedDocumentMarker::create(DocumentMarker(0, 0, false))->renderedRect());
+
+    setBodyInnerHTML("<div style='margin: 100px'>foo</div>");
+    RefPtrWillBeRawPtr<Node> text = document().body()->firstChild()->firstChild();
+    document().updateLayout();
+    markerController().addCompositionMarker(Position(text, 0), Position(text, 1), Color::black, false, Color::black);
+    markerController().addCompositionMarker(Position(text, 1), Position(text, 3), Color::black, true, Color::black);
+
+    EXPECT_EQ(2u, markerController().markers().size());
+}
+
 } // namespace blink