Add use counter for UTF-16 as a Web-exposed encoding

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 90ef2a3dccc00b3c3b50bca35a02a9f08b7bb837..a09bd98bd1d203f9b4fbef163e96d59c14757cbd 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -4117,6 +4117,11 @@ void Document::setEncodingData(const DocumentEncodingData& newData)
 
     m_encodingData = newData;
 
+    if (m_encodingData.encoding() == UTF16LittleEndianEncoding()
+        || m_encodingData.encoding() == UTF16BigEndianEncoding()) {
+        UseCounter::count(this, UseCounter::UTF16AsWebExposedEncoding);
+    }
+
     // FIXME: Should be removed as part of https://code.google.com/p/chromium/issues/detail?id=319643
     bool shouldUseVisualOrdering = m_encodingData.encoding().usesVisualOrdering();
     if (shouldUseVisualOrdering != m_visuallyOrdered) {