Import cobalt 25.master.0.1034729
diff --git a/third_party/protobuf/php/src/Google/Protobuf/Internal/MessageBuilderContext.php b/third_party/protobuf/php/src/Google/Protobuf/Internal/MessageBuilderContext.php
new file mode 100644
index 0000000..2724d26
--- /dev/null
+++ b/third_party/protobuf/php/src/Google/Protobuf/Internal/MessageBuilderContext.php
@@ -0,0 +1,120 @@
+<?php
+
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+namespace Google\Protobuf\Internal;
+
+use Google\Protobuf\Internal\GPBLabel;
+use Google\Protobuf\Internal\GPBType;
+use Google\Protobuf\Internal\Descriptor;
+use Google\Protobuf\Internal\FieldDescriptor;
+
+class MessageBuilderContext
+{
+
+    private $descriptor;
+    private $pool;
+
+    public function __construct($full_name, $klass, $pool)
+    {
+        $this->descriptor = new Descriptor();
+        $this->descriptor->setFullName($full_name);
+        $this->descriptor->setClass($klass);
+        $this->pool = $pool;
+    }
+
+    private function getFieldDescriptor($name, $label, $type,
+                                      $number, $type_name = null)
+    {
+        $field = new FieldDescriptor();
+        $field->setName($name);
+        $camel_name = implode('', array_map('ucwords', explode('_', $name)));
+        $field->setGetter('get' . $camel_name);
+        $field->setSetter('set' . $camel_name);
+        $field->setType($type);
+        $field->setNumber($number);
+        $field->setLabel($label);
+
+        // At this time, the message/enum type may have not been added to pool.
+        // So we use the type name as place holder and will replace it with the
+        // actual descriptor in cross building.
+        switch ($type) {
+        case GPBType::MESSAGE:
+          $field->setMessageType($type_name);
+          break;
+        case GPBType::ENUM:
+          $field->setEnumType($type_name);
+          break;
+        default:
+          break;
+        }
+
+        return $field;
+    }
+
+    public function optional($name, $type, $number, $type_name = null)
+    {
+        $this->descriptor->addField($this->getFieldDescriptor(
+            $name,
+            GPBLabel::OPTIONAL,
+            $type,
+            $number,
+            $type_name));
+        return $this;
+    }
+
+    public function repeated($name, $type, $number, $type_name = null)
+    {
+        $this->descriptor->addField($this->getFieldDescriptor(
+            $name,
+            GPBLabel::REPEATED,
+            $type,
+            $number,
+            $type_name));
+        return $this;
+    }
+
+    public function required($name, $type, $number, $type_name = null)
+    {
+        $this->descriptor->addField($this->getFieldDescriptor(
+            $name,
+            GPBLabel::REQUIRED,
+            $type,
+            $number,
+            $type_name));
+        return $this;
+    }
+
+    public function finalizeToPool()
+    {
+        $this->pool->addDescriptor($this->descriptor);
+    }
+}