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

third_party/protobuf/objectivec/GPBUnknownField.m

Index: third_party/protobuf/objectivec/GPBUnknownField.m
diff --git a/third_party/protobuf/objectivec/GPBUnknownField.m b/third_party/protobuf/objectivec/GPBUnknownField.m
index c49c0dfc700f3091f262649c1d75945e08ae430d..0e29bde50f66b5861d93a180fa36a5b5e1b85c37 100644
--- a/third_party/protobuf/objectivec/GPBUnknownField.m
+++ b/third_party/protobuf/objectivec/GPBUnknownField.m
@@ -31,7 +31,7 @@
 #import "GPBUnknownField_PackagePrivate.h"
 
 #import "GPBArray.h"
-#import "GPBCodedOutputStream.h"
+#import "GPBCodedOutputStream_PackagePrivate.h"
 
 @implementation GPBUnknownField {
  @protected
@@ -39,8 +39,8 @@
   GPBUInt64Array *mutableVarintList_;
   GPBUInt32Array *mutableFixed32List_;
   GPBUInt64Array *mutableFixed64List_;
-  NSMutableArray *mutableLengthDelimitedList_;
-  NSMutableArray *mutableGroupList_;
+  NSMutableArray<NSData*> *mutableLengthDelimitedList_;
+  NSMutableArray<GPBUnknownFieldSet*> *mutableGroupList_;
 }
 
 @synthesize number = number_;