StringBuilder::append should not use reserveCapacity.

third_party/WebKit/Source/wtf/text/StringBuilder.cpp

Index: third_party/WebKit/Source/wtf/text/StringBuilder.cpp
diff --git a/third_party/WebKit/Source/wtf/text/StringBuilder.cpp b/third_party/WebKit/Source/wtf/text/StringBuilder.cpp
index 10d09e5d7ecba08c91a4de15caf5ed4fcb8610ea..84b332a363985da7f054992cd3a08e1e43db11c8 100644
--- a/third_party/WebKit/Source/wtf/text/StringBuilder.cpp
+++ b/third_party/WebKit/Source/wtf/text/StringBuilder.cpp
@@ -200,9 +200,7 @@ void StringBuilder::append(const LChar* characters, unsigned length)
 
     ensureBuffer16(length);
     m_string = String();
-    m_buffer16->reserveCapacity(m_buffer16->size() + length);
-    for (size_t i = 0; i < length; ++i)
-        m_buffer16->uncheckedAppend(characters[i]);
+    m_buffer16->append(characters, length);
     m_length += length;
 }