Handle correctly "ShouldWait" result of mojo::Wait() in WebDataConsumerHandleImpl.

content/child/web_data_consumer_handle_impl_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/web_data_consumer_handle_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 264 matching lines @@
 
   run_loop.Run();
   t.Stop();
 
   EXPECT_EQ(expected, operation->result());
 }
 
 TEST_F(WebDataConsumerHandleImplTest, ZeroSizeRead) {
   ASSERT_GT(kDataPipeCapacity - 1, 0);
   constexpr size_t data_size = kDataPipeCapacity - 1;
-  std::string expected = ProduceData(data_size);
-  producer_.reset();
   std::unique_ptr<WebDataConsumerHandleImpl> handle(
       new WebDataConsumerHandleImpl(std::move(consumer_)));
   std::unique_ptr<WebDataConsumerHandle::Reader> reader(
       handle->obtainReader(nullptr));
 
   size_t read_size;
   WebDataConsumerHandle::Result rv =
       reader->read(nullptr, 0, WebDataConsumerHandle::FlagNone, &read_size);
+  EXPECT_EQ(WebDataConsumerHandle::Result::ShouldWait, rv);
+
+  std::string expected = ProduceData(data_size);
+  producer_.reset();
+
+  rv = reader->read(nullptr, 0, WebDataConsumerHandle::FlagNone, &read_size);
   EXPECT_EQ(WebDataConsumerHandle::Result::Ok, rv);
 
   char buffer[16];
   rv = reader->read(&buffer, sizeof(buffer), WebDataConsumerHandle::FlagNone,
                     &read_size);
   EXPECT_EQ(WebDataConsumerHandle::Result::Ok, rv);
   EXPECT_EQ(data_size, read_size);
   EXPECT_EQ(expected, std::string(buffer, read_size));
+
+  rv = reader->read(nullptr, 0, WebDataConsumerHandle::FlagNone, &read_size);
+  EXPECT_EQ(WebDataConsumerHandle::Result::Done, rv);
 }
 
 }  // namespace
 
 }  // namespace content