Update //third_party/protobuf to version 3.

third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java

Index: third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
diff --git a/third_party/protobuf/src/google/protobuf/unittest_optimize_for.proto b/third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
similarity index 63%
copy from third_party/protobuf/src/google/protobuf/unittest_optimize_for.proto
copy to third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
index feecbef8d4a90961b35be988402e49e74fed313c..c1997515d0fc8ac03078aecb027c3d1246ff564f 100644
--- a/third_party/protobuf/src/google/protobuf/unittest_optimize_for.proto
+++ b/third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
@@ -1,6 +1,6 @@
 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
-// http://code.google.com/p/protobuf/
+// 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
@@ -28,34 +28,28 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Author: kenton@google.com (Kenton Varda)
-//  Based on original Protocol Buffers design by
-//  Sanjay Ghemawat, Jeff Dean, and others.
-//
-// A proto file which uses optimize_for = CODE_SIZE.
-
-import "google/protobuf/unittest.proto";
-
-package protobuf_unittest;
-
-option optimize_for = CODE_SIZE;
-
-message TestOptimizedForSize {
-  optional int32 i = 1;
-  optional ForeignMessage msg = 19;
-
-  extensions 1000 to max;
-
-  extend TestOptimizedForSize {
-    optional int32 test_extension = 1234;
-    optional TestRequiredOptimizedForSize test_extension2 = 1235;
+package com.google.protobuf;
+
+import java.nio.ByteBuffer;
+
+/**
+ * Provides unsafe factory methods for {@link ByteString} instances.
+ *
+ * <p><strong>DISCLAIMER:</strong> The methods in this class should only be called if it is
+ * guaranteed that the the buffer backing the {@link ByteString} will never change! Mutation of a
+ * {@link ByteString} can lead to unexpected and undesirable consequences in your application,
+ * and will likely be difficult to debug. Proceed with caution!
+ */
+public final class UnsafeByteStrings {
+  private UnsafeByteStrings() {}
+
+  /**
+   * An unsafe operation that returns a {@link ByteString} that is backed by the provided buffer.
+   *
+   * @param buffer the Java NIO buffer to be wrapped.
+   * @return a {@link ByteString} backed by the provided buffer.
+   */
+  public static ByteString unsafeWrap(ByteBuffer buffer) {
+    return new NioByteString(buffer);
   }
 }
-
-message TestRequiredOptimizedForSize {
-  required int32 x = 1;
-}
- 
-message TestOptionalOptimizedForSize {
-  optional TestRequiredOptimizedForSize o = 1;
-}