Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h

Index: third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h
diff --git a/third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h b/third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h
index 02d0e16e7a8018d4f29137f46204f140929c36dd..478db2cf0f96395915637ab862a0ec2f29a2bc1c 100644
--- a/third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h
+++ b/third_party/protobuf/objectivec/GPBMessage_PackagePrivate.h
@@ -78,6 +78,10 @@ typedef struct GPBMessage_Storage *GPBMessage_StoragePtr;
 // returns nil if the extension is not set)
 - (id)getExistingExtension:(GPBExtensionDescriptor *)extension;
 
+// Returns an array of GPBExtensionDescriptor* for all the extensions currently
+// in use on the message.  They are sorted by field number.
+- (NSArray *)sortedExtensionsInUse;
+
 // Parses a message of this type from the input and merges it with this
 // message.
 //
@@ -106,12 +110,9 @@ CF_EXTERN_C_BEGIN
 
 // Call this before using the readOnlySemaphore_. This ensures it is created only once.
 NS_INLINE void GPBPrepareReadOnlySemaphore(GPBMessage *self) {
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdirect-ivar-access"
   dispatch_once(&self->readOnlySemaphoreCreationOnce_, ^{
     self->readOnlySemaphore_ = dispatch_semaphore_create(1);
   });
-#pragma clang diagnostic pop
 }
 
 // Returns a new instance that was automatically created by |autocreator| for