Migrate WTF::Deque::last() to ::back()

third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp

Index: third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp
diff --git a/third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp b/third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp
index 49aabbab815c9baa1c8e1ee35789e4ae95bc9264..0876b64691c4b67570f593cf49e604b2b070e2b2 100644
--- a/third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp
+++ b/third_party/WebKit/Source/core/editing/spellcheck/SpellCheckRequester.cpp
@@ -207,7 +207,7 @@ void SpellCheckRequester::enqueueRequest(SpellCheckRequest* request) {
   DCHECK(request);
   bool continuation = false;
   if (!m_requestQueue.isEmpty()) {
-    SpellCheckRequest* lastRequest = m_requestQueue.last();
+    SpellCheckRequest* lastRequest = m_requestQueue.back();
     // It's a continuation if the number of the last request got incremented in
     // the new one and both apply to the same editable.
     continuation =