Factor and simplify generation of the lookup trie used for HTMLLookupTrie.

third_party/WebKit/Source/build/scripts/templates/ElementLookupTrie.cpp.tmpl

-{% from 'macros.tmpl' import license %}
-{{license()}}
-{% macro trie_switch(trie, index) %}
-{# FIXME: No need to switch if there's only a single item in the subtrie:
-   can just have an if statement as we're currently doing for leaves. #}
-switch (data[{{index}}]) {
-{% for char, subtrie, tag, conditions in trie %}
-case '{{char}}':
-    {% if subtrie %}{# Recurse on subtrie #}
-    {{trie_switch(subtrie, index + 1) | indent}}
-    {% elif conditions %}{# Check suffix #}
-    if ({{conditions | join(' && ')}})
-        return {{tag}}Tag.localName().impl();
-    return 0;
-    {% else %}{# Terminal node (no suffix) #}
-    return {{tag}}Tag.localName().impl();
-    {% endif %}
-{% endfor %}
-}
-return 0;
-{% endmacro %}
+{% from 'macros.tmpl' import trie_length_switch %}
+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
 
 #include "{{namespace}}ElementLookupTrie.h"
 
 #include "{{namespace}}Names.h"
 
 namespace blink {
 
 using namespace {{namespace}}Names;
 
 StringImpl* lookup{{namespace}}Tag(const UChar* data, unsigned length)
 {
-    ASSERT(data);
-    ASSERT(length);
-    switch (length) {
-    {% for length, trie in length_tries %}
-    case {{length}}:
-        {{trie_switch(trie, 0) | indent(8)}}
-    {% endfor %}
-    }
-    return 0;
+    DCHECK(data);
+    DCHECK(length);
+    {% macro trie_return_statement(tag) %}{{tag}}Tag.localName().impl(){% endmacro %}
+    {{ trie_length_switch(length_tries, trie_return_statement, 'nullptr') | indent(4) }}
+    return nullptr;
 }
 
 } // namespace blink