Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/java/core/src/main/java/com/google/protobuf/ExperimentalApi.java

Index: third_party/protobuf/java/core/src/main/java/com/google/protobuf/ExperimentalApi.java
diff --git a/third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java b/third_party/protobuf/java/core/src/main/java/com/google/protobuf/ExperimentalApi.java
similarity index 62%
copy from third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
copy to third_party/protobuf/java/core/src/main/java/com/google/protobuf/ExperimentalApi.java
index c1997515d0fc8ac03078aecb027c3d1246ff564f..3cd4c88492862d6e06e88a6e869e00e543ead293 100644
--- a/third_party/protobuf/java/src/main/java/com/google/protobuf/UnsafeByteStrings.java
+++ b/third_party/protobuf/java/core/src/main/java/com/google/protobuf/ExperimentalApi.java
@@ -30,26 +30,37 @@
 
 package com.google.protobuf;
 
-import java.nio.ByteBuffer;
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
 
 /**
- * Provides unsafe factory methods for {@link ByteString} instances.
+ * Indicates a public API that can change at any time, and has no guarantee of API stability and
+ * backward-compatibility.
  *
- * <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!
+ * <p>Usage guidelines:
+ * <ol>
+ * <li>This annotation is used only on public API. Internal interfaces should not use it.</li>
+ * <li>This annotation should only be added to new APIs. Adding it to an existing API is
+ * considered API-breaking.</li>
+ * <li>Removing this annotation from an API gives it stable status.</li>
+ * </ol>
  */
-public final class UnsafeByteStrings {
-  private UnsafeByteStrings() {}
-
+@Retention(RetentionPolicy.SOURCE)
+@Target({
+    ElementType.ANNOTATION_TYPE,
+    ElementType.CONSTRUCTOR,
+    ElementType.FIELD,
+    ElementType.METHOD,
+    ElementType.PACKAGE,
+    ElementType.TYPE})
+@Documented
+public @interface ExperimentalApi {
   /**
-   * 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.
+   * Context information such as links to discussion thread, tracking issue etc.
    */
-  public static ByteString unsafeWrap(ByteBuffer buffer) {
-    return new NioByteString(buffer);
-  }
+  String value() default "";
 }
+