third_party/protobuf: Update to HEAD (f52e188fe4)

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

 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // 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
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
@@ skipping 279 matching lines @@
       @Override
       public DynamicMessage parsePartialFrom(
           CodedInputStream input, ExtensionRegistryLite extensionRegistry)
           throws InvalidProtocolBufferException {
         Builder builder = newBuilder(type);
         try {
           builder.mergeFrom(input, extensionRegistry);
         } catch (InvalidProtocolBufferException e) {
           throw e.setUnfinishedMessage(builder.buildPartial());
         } catch (IOException e) {
-          throw new InvalidProtocolBufferException(e.getMessage())
+          throw new InvalidProtocolBufferException(e)
               .setUnfinishedMessage(builder.buildPartial());
         }
         return builder.buildPartial();
       }
     };
   }
 
   /** Verifies that the field is a field of this message. */
   private void verifyContainingType(FieldDescriptor field) {
     if (field.getContainingType() != type) {
@@ skipping 208 matching lines @@
         ensureEnumValueDescriptor(field, value);
       }
       OneofDescriptor oneofDescriptor = field.getContainingOneof();
       if (oneofDescriptor != null) {
         int index = oneofDescriptor.getIndex();
         FieldDescriptor oldField = oneofCases[index];
         if ((oldField != null) && (oldField != field)) {
           fields.clearField(oldField);
         }
         oneofCases[index] = field;
+      } else if (field.getFile().getSyntax() == Descriptors.FileDescriptor.Syntax.PROTO3) {
+        if (!field.isRepeated()
+            && field.getJavaType() != FieldDescriptor.JavaType.MESSAGE
+            && value.equals(field.getDefaultValue())) {
+          // In proto3, setting a field to its default value is equivalent to clearing the field.
+          fields.clearField(field);
+          return this;
+        }
       }
       fields.setField(field, value);
       return this;
     }
 
     @Override
     public Builder clearField(FieldDescriptor field) {
       verifyContainingType(field);
       ensureIsMutable();
       OneofDescriptor oneofDescriptor = field.getContainingOneof();
@@ skipping 128 matching lines @@
     }
 
     @Override
     public com.google.protobuf.Message.Builder getRepeatedFieldBuilder(FieldDescriptor field,
         int index) {
       throw new UnsupportedOperationException(
         "getRepeatedFieldBuilder() called on a dynamic message type.");
     }
   }
 }