Add WARN_UNUSED_RESULT to BytesConsumer read methods.

third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp

Index: third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp
diff --git a/third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp b/third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp
index 0ab8960df2e46f01cbd3a55ec36aa37b4422cb8e..27267d9945b09f9b04488c684b82d7ea85bbc1f1 100644
--- a/third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp
+++ b/third_party/WebKit/Source/modules/fetch/BytesConsumerTestUtil.cpp
@@ -209,7 +209,10 @@ void BytesConsumerTestUtil::TwoPhaseReader::onStateChange()
             // because of the same reasons as Reader::onStateChange.
             size_t read = std::max(static_cast<size_t>(3), available);
             m_data.append(buffer, read);
-            m_consumer->endRead(read);
+            if (m_consumer->endRead(read) != BytesConsumer::Result::Ok) {
+                m_result = BytesConsumer::Result::Error;
+                return;
+            }
             break;
         }
         case BytesConsumer::Result::ShouldWait: