Update message framing IDs to adhere to gRPC spec

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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=69657434
diff --git a/core/src/main/java/com/google/net/stubby/GrpcFramingUtil.java b/core/src/main/java/com/google/net/stubby/GrpcFramingUtil.java
index 2ec545f..33e19df 100644
--- a/core/src/main/java/com/google/net/stubby/GrpcFramingUtil.java
+++ b/core/src/main/java/com/google/net/stubby/GrpcFramingUtil.java
@@ -27,8 +27,8 @@
   // Flags
   public static final byte PAYLOAD_FRAME = 0x0;
   public static final byte CONTEXT_VALUE_FRAME =  0x1;
-  public static final byte STATUS_FRAME = 0x2;
-  public static final byte RESERVED_FRAME = 0x3;
+  public static final byte CALL_HEADER_FRAME = 0x2;
+  public static final byte STATUS_FRAME = 0x3;
   public static final byte FRAME_TYPE_MASK = 0x3;
 
   /**