Adapt to upstream Spring Framework changes

Author: philwebb

Diff for: spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/reactive/result/view/MustacheView.java

@@ -34,6 +34,7 @@
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.http.MediaType;
 import org.springframework.web.reactive.result.view.AbstractUrlBasedView;
 import org.springframework.web.reactive.result.view.View;
@@ -81,7 +82,8 @@ protected Mono<Void> renderInternal(Map<String, Object> model, MediaType content
 			return Mono
 					.error(new IllegalStateException("Could not find Mustache template with URL [" + getUrl() + "]"));
 		}
-		DataBuffer dataBuffer = exchange.getResponse().bufferFactory().allocateBuffer();
+		DataBuffer dataBuffer = exchange.getResponse().bufferFactory()
+				.allocateBuffer(DefaultDataBufferFactory.DEFAULT_INITIAL_CAPACITY);
 		try (Reader reader = getReader(resource)) {
 			Template template = this.compiler.compile(reader);
 			Charset charset = getCharset(contentType).orElseGet(this::getDefaultCharset);