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 e1922ae1bc21f92362cc71e10faff7116bf4a6ff..ca46c07e4e2d1e5ddfee4310676fe93071d28823 100644
--- a/third_party/WebKit/Source/wtf/text/StringBuilder.cpp
+++ b/third_party/WebKit/Source/wtf/text/StringBuilder.cpp
@@ -191,9 +191,7 @@ void StringBuilder::append(const LChar* characters, unsigned length)
 
     ensureBuffer16();
     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;
 }