[Blob] BlobReader class & tests, and removal of all redundant reading.

content/browser/fileapi/blob_reader_unittest.cc

Index: content/browser/fileapi/blob_reader_unittest.cc
diff --git a/content/browser/fileapi/blob_reader_unittest.cc b/content/browser/fileapi/blob_reader_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1efe4ead74b44e5797936ccc6f75f34ca86c1908
--- /dev/null
+++ b/content/browser/fileapi/blob_reader_unittest.cc
@@ -0,0 +1,1104 @@
+// Copyright 2015 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 "storage/browser/blob/blob_reader.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/location.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/strings/stringprintf.h"
+#include "base/task_runner.h"
+#include "base/time/time.h"
+#include "content/public/test/async_file_test_helper.h"
+#include "content/public/test/test_file_system_context.h"
+#include "net/base/completion_callback.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+#include "net/base/test_completion_callback.h"
+#include "net/disk_cache/disk_cache.h"
+#include "storage/browser/blob/blob_data_builder.h"
+#include "storage/browser/blob/blob_data_handle.h"
+#include "storage/browser/blob/blob_storage_context.h"
+#include "storage/browser/fileapi/file_stream_reader.h"
+#include "storage/browser/fileapi/file_system_context.h"
+#include "storage/browser/fileapi/file_system_file_util.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+using base::FilePath;
+using content::AsyncFileTestHelper;
+using net::DrainableIOBuffer;
+using net::IOBuffer;
+
+namespace storage {
+namespace {
+
+const int kTestDiskCacheStreamIndex = 0;
+
+// Our disk cache tests don't need a real data handle since the tests themselves
+// scope the disk cache and entries.
+class EmptyDataHandle : public storage::BlobDataBuilder::DataHandle {
+ private:
+  ~EmptyDataHandle() override {}
+};
+
+// A disk_cache::Entry that arbitrarily delays the completion of a read
+// operation to allow testing some races without flake. This is particularly
+// relevant in this unit test, which uses the always-synchronous MEMORY_CACHE.
+class DelayedReadEntry : public disk_cache::Entry {
+ public:
+  explicit DelayedReadEntry(disk_cache::ScopedEntryPtr entry)
+      : entry_(entry.Pass()) {}
+  ~DelayedReadEntry() override { EXPECT_FALSE(HasPendingReadCallbacks()); }
+
+  bool HasPendingReadCallbacks() { return !pending_read_callbacks_.empty(); }
+
+  void RunPendingReadCallbacks() {
+    std::vector<base::Callback<void(void)>> callbacks;
+    pending_read_callbacks_.swap(callbacks);
+    for (const auto& callback : callbacks)
+      callback.Run();
+  }
+
+  // From disk_cache::Entry:
+  void Doom() override { entry_->Doom(); }
+
+  void Close() override { delete this; }  // Note this is required by the API.
+
+  std::string GetKey() const override { return entry_->GetKey(); }
+
+  base::Time GetLastUsed() const override { return entry_->GetLastUsed(); }
+
+  base::Time GetLastModified() const override {
+    return entry_->GetLastModified();
+  }
+
+  int32 GetDataSize(int index) const override {
+    return entry_->GetDataSize(index);
+  }
+
+  int ReadData(int index,
+               int offset,
+               IOBuffer* buf,
+               int buf_len,
+               const CompletionCallback& original_callback) override {
+    net::TestCompletionCallback callback;
+    int rv = entry_->ReadData(index, offset, buf, buf_len, callback.callback());
+    DCHECK_NE(rv, net::ERR_IO_PENDING)
+        << "Test expects to use a MEMORY_CACHE instance, which is synchronous.";
+    pending_read_callbacks_.push_back(base::Bind(original_callback, rv));
+    return net::ERR_IO_PENDING;
+  }
+
+  int WriteData(int index,
+                int offset,
+                IOBuffer* buf,
+                int buf_len,
+                const CompletionCallback& callback,
+                bool truncate) override {
+    return entry_->WriteData(index, offset, buf, buf_len, callback, truncate);
+  }
+
+  int ReadSparseData(int64 offset,
+                     IOBuffer* buf,
+                     int buf_len,
+                     const CompletionCallback& callback) override {
+    return entry_->ReadSparseData(offset, buf, buf_len, callback);
+  }
+
+  int WriteSparseData(int64 offset,
+                      IOBuffer* buf,
+                      int buf_len,
+                      const CompletionCallback& callback) override {
+    return entry_->WriteSparseData(offset, buf, buf_len, callback);
+  }
+
+  int GetAvailableRange(int64 offset,
+                        int len,
+                        int64* start,
+                        const CompletionCallback& callback) override {
+    return entry_->GetAvailableRange(offset, len, start, callback);
+  }
+
+  bool CouldBeSparse() const override { return entry_->CouldBeSparse(); }
+
+  void CancelSparseIO() override { entry_->CancelSparseIO(); }
+
+  int ReadyForSparseIO(const CompletionCallback& callback) override {
+    return entry_->ReadyForSparseIO(callback);
+  }
+
+ private:
+  disk_cache::ScopedEntryPtr entry_;
+  std::vector<base::Callback<void(void)>> pending_read_callbacks_;
+};
+
+scoped_ptr<disk_cache::Backend> CreateInMemoryDiskCache(
+    const scoped_refptr<base::SingleThreadTaskRunner>& thread) {
+  scoped_ptr<disk_cache::Backend> cache;
+  net::TestCompletionCallback callback;
+  int rv = disk_cache::CreateCacheBackend(
+      net::MEMORY_CACHE, net::CACHE_BACKEND_DEFAULT, FilePath(), 0, false,
+      thread, nullptr, &cache, callback.callback());
+  EXPECT_EQ(net::OK, callback.GetResult(rv));
+
+  return cache.Pass();
+}
+
+disk_cache::ScopedEntryPtr CreateDiskCacheEntry(disk_cache::Backend* cache,
+                                                const char* key,
+                                                const std::string& data) {
+  disk_cache::Entry* temp_entry = nullptr;
+  net::TestCompletionCallback callback;
+  int rv = cache->CreateEntry(key, &temp_entry, callback.callback());
+  if (callback.GetResult(rv) != net::OK)
+    return nullptr;
+  disk_cache::ScopedEntryPtr entry(temp_entry);
+
+  scoped_refptr<net::StringIOBuffer> iobuffer = new net::StringIOBuffer(data);
+  rv = entry->WriteData(kTestDiskCacheStreamIndex, 0, iobuffer.get(),
+                        iobuffer->size(), callback.callback(), false);
+  EXPECT_EQ(static_cast<int>(data.size()), callback.GetResult(rv));
+  return entry.Pass();
+}
+
+template <typename T>
+void SetValue(T* address, T value) {
+  *address = value;
+}
+
+class FakeFileStreamReader : public FileStreamReader {
+ public:
+  explicit FakeFileStreamReader(const std::string& contents)
+      : buffer_(new DrainableIOBuffer(
+            new net::StringIOBuffer(
+                scoped_ptr<std::string>(new std::string(contents))),
+            contents.size())),
+        net_error_(net::OK),
+        size_(contents.size()) {}
+  FakeFileStreamReader(const std::string& contents, uint64_t size)
+      : buffer_(new DrainableIOBuffer(
+            new net::StringIOBuffer(
+                scoped_ptr<std::string>(new std::string(contents))),
+            contents.size())),
+        net_error_(net::OK),
+        size_(size) {}
+
+  void ReturnError(int net_error) { net_error_ = net_error; }
+
+  void DoAsync(base::SingleThreadTaskRunner* runner) {
+    async_task_runner_ = runner;
+  }
+
+  ~FakeFileStreamReader() override {}
+
+  int Read(net::IOBuffer* buf,
+           int buf_length,
+           const net::CompletionCallback& done) override {
+    if (net_error_ == net::OK) {
+      if (async_task_runner_.get()) {
+        async_task_runner_->PostTask(
+            FROM_HERE,
+            base::Bind(base::IgnoreResult(&FakeFileStreamReader::ReadImpl),
+                       base::Unretained(this), scoped_refptr<IOBuffer>(buf),
+                       buf_length, done));
+        return net::ERR_IO_PENDING;
+      } else {
+        return ReadImpl(buf, buf_length, net::CompletionCallback());
+      }
+    }
+    if (async_task_runner_.get()) {
+      async_task_runner_->PostTask(FROM_HERE, base::Bind(done, net_error_));
+      return net::ERR_IO_PENDING;
+    }
+    return net_error_;
+  }
+
+  int64 GetLength(const net::Int64CompletionCallback& size_callback) override {
+    if (net_error_ == net::OK) {
+      if (async_task_runner_.get()) {
+        async_task_runner_->PostTask(
+            FROM_HERE,
+            base::Bind(base::IgnoreResult(&FakeFileStreamReader::GetLengthImpl),
+                       base::Unretained(this), size_callback));
+        return net::ERR_IO_PENDING;
+      } else {
+        return GetLengthImpl(net::Int64CompletionCallback());
+      }
+    }
+    if (async_task_runner_.get()) {
+      async_task_runner_->PostTask(
+          FROM_HERE,
+          base::Bind(size_callback, static_cast<int64_t>(net_error_)));
+      return net::ERR_IO_PENDING;
+    }
+    return net_error_;
+  }
+
+ private:
+  int ReadImpl(scoped_refptr<net::IOBuffer> buf,
+               int buf_length,
+               const net::CompletionCallback& done) {
+    CHECK_GE(buf_length, 0);
+    int length = std::min(buf_length, buffer_->BytesRemaining());
+    memcpy(buf->data(), buffer_->data(), length);
+    buffer_->DidConsume(length);
+    if (done.is_null()) {
+      return length;
+    }
+    done.Run(length);
+    return net::ERR_IO_PENDING;
+  }
+
+  int64 GetLengthImpl(const net::Int64CompletionCallback& size_callback) {
+    if (size_callback.is_null()) {
+      return size_;
+    }
+    size_callback.Run(size_);
+    return net::ERR_IO_PENDING;
+  }
+
+  scoped_refptr<net::DrainableIOBuffer> buffer_;
+  scoped_refptr<base::SingleThreadTaskRunner> async_task_runner_;
+  int net_error_;
+  uint64_t size_;
+
+  DISALLOW_COPY_AND_ASSIGN(FakeFileStreamReader);
+};
+
+class MockFileStreamReaderProvider
+    : public BlobReader::FileStreamReaderProvider {
+ public:
+  ~MockFileStreamReaderProvider() override {}
+
+  MOCK_METHOD4(CreateForLocalFile,
+               FileStreamReader*(base::TaskRunner* task_runner,
+                                 const FilePath& file_path,
+                                 int64_t initial_offset,
+                                 const base::Time& expected_modification_time));
+  MOCK_METHOD4(CreateFileStreamReader,
+               FileStreamReader*(const GURL& filesystem_url,
+                                 int64_t offset,
+                                 int64_t max_bytes_to_read,
+                                 const base::Time& expected_modification_time));
+};
+
+}  // namespace
+
+class BlobReaderTest : public ::testing::Test {
+ public:
+  BlobReaderTest() {}
+  ~BlobReaderTest() override {}
+
+  void TearDown() override { base::RunLoop().RunUntilIdle(); }
+
+ protected:
+  void InitializeReader(BlobDataBuilder* builder) {
+    blob_handle_ = builder ? context_.AddFinishedBlob(builder).Pass() : nullptr;
+    provider_ = new MockFileStreamReaderProvider();
+    scoped_ptr<BlobReader::FileStreamReaderProvider> temp_ptr(provider_);
+    reader_.reset(new BlobReader(blob_handle_.get(), temp_ptr.Pass(),
+                                 message_loop_.task_runner().get()));
+  }
+
+  // Takes ownership of the file reader (the blob reader takes ownership).
+  void ExpectLocalFileCall(const FilePath& file_path,
+                           base::Time modification_time,
+                           uint64_t initial_offset,
+                           FakeFileStreamReader* reader) {
+    EXPECT_CALL(*provider_,
+                CreateForLocalFile(message_loop_.task_runner().get(), file_path,
+                                   initial_offset, modification_time))
+        .WillOnce(testing::Return(reader));
+  }
+
+  // Takes ownership of the file reader (the blob reader takes ownership).
+  void ExpectFileSystemCall(const GURL& filesystem_url,
+                            int64_t offset,
+                            int64_t max_bytes_to_read,
+                            base::Time expected_modification_time,
+                            FakeFileStreamReader* reader) {
+    EXPECT_CALL(*provider_, CreateFileStreamReader(filesystem_url, offset,
+                                                   max_bytes_to_read,
+                                                   expected_modification_time))
+        .WillOnce(testing::Return(reader));
+  }
+
+  void CheckSizeCalculatedSynchronously(size_t expected_size, int async_size) {
+    EXPECT_EQ(-1, async_size);
+    EXPECT_EQ(net::OK, reader_->net_error());
+    EXPECT_EQ(expected_size, reader_->total_size());
+    EXPECT_TRUE(reader_->total_size_calculated());
+  }
+
+  void CheckSizeNotCalculatedYet(int async_size) {
+    EXPECT_EQ(-1, async_size);
+    EXPECT_EQ(net::OK, reader_->net_error());
+    EXPECT_FALSE(reader_->total_size_calculated());
+  }
+
+  void CheckSizeCalculatedAsynchronously(size_t expected_size, int async_size) {
+    EXPECT_EQ(expected_size, static_cast<size_t>(async_size));
+    EXPECT_EQ(net::OK, reader_->net_error());
+    EXPECT_EQ(expected_size, reader_->total_size());
+    EXPECT_TRUE(reader_->total_size_calculated());
+  }
+
+  scoped_refptr<net::IOBuffer> CreateBuffer(uint64_t size) {
+    return scoped_refptr<net::IOBuffer>(
+        new net::IOBuffer(static_cast<size_t>(size)));
+  }
+
+  bool IsReaderTotalSizeCalculated() {
+    return reader_->total_size_calculated();
+  }
+
+  BlobStorageContext context_;
+  scoped_ptr<BlobDataHandle> blob_handle_;
+  MockFileStreamReaderProvider* provider_ = nullptr;
+  base::MessageLoop message_loop_;
+  scoped_ptr<BlobReader> reader_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BlobReaderTest);
+};
+
+namespace {
+
+TEST_F(BlobReaderTest, BasicMemory) {
+  BlobDataBuilder b("uuid");
+  const std::string kData("Hello!!!");
+  const size_t kDataSize = 8ul;
+  b.AppendData(kData);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kDataSize, calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kDataSize));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kDataSize, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kDataSize, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "Hello!!!", kDataSize));
+}
+
+TEST_F(BlobReaderTest, BasicFile) {
+  BlobDataBuilder b("uuid");
+  const FilePath kPath = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+  b.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&b);
+
+  // Non-async reader.
+  ExpectLocalFileCall(kPath, kTime, 0, new FakeFileStreamReader(kData));
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kData.size(), static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "FileData!!!", kData.size()));
+}
+
+TEST_F(BlobReaderTest, BasicFileSystem) {
+  BlobDataBuilder b("uuid");
+  const GURL kURL("file://test_file/here.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+  b.AppendFileSystemFile(kURL, 0, kData.size(), kTime);
+  this->InitializeReader(&b);
+
+  // Non-async reader.
+  ExpectFileSystemCall(kURL, 0, kData.size(), kTime,
+                       new FakeFileStreamReader(kData));
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kData.size(), static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "FileData!!!", kData.size()));
+}
+
+TEST_F(BlobReaderTest, BasicDiskCache) {
+  scoped_ptr<disk_cache::Backend> cache =
+      CreateInMemoryDiskCache(message_loop_.task_runner());
+  ASSERT_TRUE(cache);
+
+  BlobDataBuilder b("uuid");
+  const std::string kData = "Test Blob Data";
+  scoped_refptr<BlobDataBuilder::DataHandle> data_handle =
+      new EmptyDataHandle();
+  disk_cache::ScopedEntryPtr entry =
+      CreateDiskCacheEntry(cache.get(), "test entry", kData);
+  b.AppendDiskCacheEntry(data_handle, entry.get(), kTestDiskCacheStreamIndex);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kData.size(), static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "Test Blob Data", kData.size()));
+}
+
+TEST_F(BlobReaderTest, BufferLargerThanMemory) {
+  BlobDataBuilder b("uuid");
+  const std::string kData("Hello!!!");
+  const size_t kDataSize = 8ul;
+  const size_t kBufferSize = 10ul;
+  b.AppendData(kData);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kBufferSize));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kBufferSize, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kDataSize, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "Hello!!!", kDataSize));
+}
+
+TEST_F(BlobReaderTest, MemoryRange) {
+  BlobDataBuilder b("uuid");
+  const std::string kData("Hello!!!");
+  const size_t kDataSize = 8ul;
+  const size_t kSeekOffset = 2ul;
+  const uint64_t kReadLength = 4ull;
+  b.AppendData(kData);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(kReadLength);
+
+  reader_->SetReadRange(kSeekOffset, kReadLength);
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kDataSize - kSeekOffset, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kReadLength, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "llo!", kReadLength));
+}
+
+TEST_F(BlobReaderTest, BufferSmallerThanMemory) {
+  BlobDataBuilder b("uuid");
+  const std::string kData("Hello!!!");
+  const size_t kBufferSize = 4ul;
+  b.AppendData(kData);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kBufferSize));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kBufferSize, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kBufferSize, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "Hell", kBufferSize));
+
+  bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kBufferSize, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kBufferSize, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "o!!!", kBufferSize));
+}
+
+TEST_F(BlobReaderTest, SegmentedBufferAndMemory) {
+  BlobDataBuilder b("uuid");
+  const size_t kNumItems = 10;
+  const size_t kItemSize = 6;
+  const size_t kBufferSize = 10;
+  const size_t kTotalSize = kNumItems * kItemSize;
+  char current_value = 0;
+  for (size_t i = 0; i < kNumItems; i++) {
+    char buf[kItemSize];
+    for (size_t j = 0; j < kItemSize; j++) {
+      buf[j] = current_value++;
+    }
+    b.AppendData(buf, kItemSize);
+  }
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kTotalSize, calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kBufferSize));
+
+  current_value = 0;
+  for (size_t i = 0; i < kTotalSize / kBufferSize; i++) {
+    int bytes_read = 0;
+    int async_bytes_read = 0;
+    EXPECT_EQ(BlobReader::Status::DONE,
+              reader_->Read(buffer.get(), kBufferSize, &bytes_read,
+                            base::Bind(&SetValue<int>, &async_bytes_read)));
+    EXPECT_EQ(net::OK, reader_->net_error());
+    EXPECT_EQ(kBufferSize, static_cast<size_t>(bytes_read));
+    EXPECT_EQ(0, async_bytes_read);
+    for (size_t j = 0; j < kBufferSize; j++) {
+      EXPECT_EQ(current_value, buffer->data()[j]);
+      current_value++;
+    }
+  }
+}
+
+TEST_F(BlobReaderTest, FileAsync) {
+  BlobDataBuilder b("uuid");
+  const FilePath kPath = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+  b.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&b);
+
+  scoped_ptr<FakeFileStreamReader> reader(new FakeFileStreamReader(kData));
+  reader->DoAsync(message_loop_.task_runner().get());
+
+  ExpectLocalFileCall(kPath, kTime, 0, reader.release());
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  CheckSizeNotCalculatedYet(calculated_size);
+  message_loop_.RunUntilIdle();
+  CheckSizeCalculatedAsynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kData.size(), static_cast<size_t>(async_bytes_read));
+  EXPECT_EQ(0, bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "FileData!!!", kData.size()));
+}
+
+TEST_F(BlobReaderTest, FileSystemAsync) {
+  BlobDataBuilder b("uuid");
+  const GURL kURL("file://test_file/here.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+  b.AppendFileSystemFile(kURL, 0, kData.size(), kTime);
+  this->InitializeReader(&b);
+
+  scoped_ptr<FakeFileStreamReader> reader(new FakeFileStreamReader(kData));
+  reader->DoAsync(message_loop_.task_runner().get());
+
+  ExpectFileSystemCall(kURL, 0, kData.size(), kTime, reader.release());
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  CheckSizeNotCalculatedYet(calculated_size);
+  message_loop_.RunUntilIdle();
+  CheckSizeCalculatedAsynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kData.size(), static_cast<size_t>(async_bytes_read));
+  EXPECT_EQ(0, bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "FileData!!!", kData.size()));
+}
+
+TEST_F(BlobReaderTest, DiskCacheAsync) {
+  scoped_ptr<disk_cache::Backend> cache =
+      CreateInMemoryDiskCache(message_loop_.task_runner());
+  ASSERT_TRUE(cache);
+
+  BlobDataBuilder b("uuid");
+  const std::string kData = "Test Blob Data";
+  scoped_refptr<BlobDataBuilder::DataHandle> data_handle =
+      new EmptyDataHandle();
+  scoped_ptr<DelayedReadEntry> delayed_read_entry(new DelayedReadEntry(
+      CreateDiskCacheEntry(cache.get(), "test entry", kData).Pass()));
+  b.AppendDiskCacheEntry(data_handle, delayed_read_entry.get(),
+                         kTestDiskCacheStreamIndex);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  CheckSizeCalculatedSynchronously(kData.size(), calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_TRUE(delayed_read_entry->HasPendingReadCallbacks());
+  delayed_read_entry->RunPendingReadCallbacks();
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(0, bytes_read);
+  EXPECT_EQ(kData.size(), static_cast<size_t>(async_bytes_read));
+  EXPECT_EQ(0, memcmp(buffer->data(), "Test Blob Data", kData.size()));
+}
+
+TEST_F(BlobReaderTest, FileRange) {
+  BlobDataBuilder b("uuid");
+  const FilePath kPath = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  // We check the offset in the ExpectLocalFileCall mock.
+  const std::string kRangeData = "leD";
+  const std::string kData = "FileData!!!";
+  const uint64_t kOffset = 2;
+  const uint64_t kReadLength = 3;
+  const base::Time kTime = base::Time::Now();
+  b.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&b);
+
+  scoped_ptr<FakeFileStreamReader> reader(new FakeFileStreamReader(kData));
+  reader->DoAsync(message_loop_.task_runner().get());
+  ExpectLocalFileCall(kPath, kTime, 0, reader.release());
+
+  // We create the reader again with the offset after the seek.
+  reader.reset(new FakeFileStreamReader(kRangeData));
+  reader->DoAsync(message_loop_.task_runner().get());
+  ExpectLocalFileCall(kPath, kTime, kOffset, reader.release());
+
+  int calculated_size = -1;
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  message_loop_.RunUntilIdle();
+
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(kReadLength);
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->SetReadRange(kOffset, kReadLength));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kReadLength, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kReadLength, static_cast<size_t>(async_bytes_read));
+  EXPECT_EQ(0, bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "leD", kReadLength));
+}
+
+TEST_F(BlobReaderTest, DiskCacheRange) {
+  scoped_ptr<disk_cache::Backend> cache =
+      CreateInMemoryDiskCache(message_loop_.task_runner());
+  ASSERT_TRUE(cache);
+
+  BlobDataBuilder b("uuid");
+  const std::string kData = "Test Blob Data";
+  const uint64_t kOffset = 2;
+  const uint64_t kReadLength = 3;
+  scoped_refptr<BlobDataBuilder::DataHandle> data_handle =
+      new EmptyDataHandle();
+  disk_cache::ScopedEntryPtr entry =
+      CreateDiskCacheEntry(cache.get(), "test entry", kData);
+  b.AppendDiskCacheEntry(data_handle, entry.get(), kTestDiskCacheStreamIndex);
+  this->InitializeReader(&b);
+
+  int calculated_size = -1;
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(kReadLength);
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->SetReadRange(kOffset, kReadLength));
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::DONE,
+            reader_->Read(buffer.get(), kReadLength, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(kReadLength, static_cast<size_t>(bytes_read));
+  EXPECT_EQ(0, async_bytes_read);
+  EXPECT_EQ(0, memcmp(buffer->data(), "st ", kReadLength));
+}
+
+TEST_F(BlobReaderTest, FileSomeAsyncSegmentedOffsetsUnknownSizes) {
+  // This tests includes:
+  // * Unknown file sizes (item length of uint64::max) for every other item.
+  // * Offsets for every 3rd file item.
+  // * Non-async reader for every 4th file item.
+  BlobDataBuilder b("uuid");
+  const FilePath kPathBase = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  const base::Time kTime = base::Time::Now();
+  const size_t kNumItems = 10;
+  const size_t kItemSize = 6;
+  const size_t kBufferSize = 10;
+  const size_t kTotalSize = kNumItems * kItemSize;
+  char current_value = 0;
+  // Create blob and reader.
+  for (size_t i = 0; i < kNumItems; i++) {
+    current_value += kItemSize;
+    FilePath path = kPathBase.Append(
+        FilePath::FromUTF8Unsafe(base::StringPrintf("%d", current_value)));
+    uint64_t offset = i % 3 == 0 ? 1 : 0;
+    uint64_t size =
+        i % 2 == 0 ? kItemSize : std::numeric_limits<uint64_t>::max();
+    b.AppendFile(path, offset, size, kTime);
+  }
+  this->InitializeReader(&b);
+
+  // Set expectations.
+  current_value = 0;
+  for (size_t i = 0; i < kNumItems; i++) {
+    uint64_t offset = i % 3 == 0 ? 1 : 0;
+    char buf[kItemSize + offset];
+    if (offset > 0) {
+      memset(buf, 7, offset);
+    }
+    for (size_t j = 0; j < kItemSize; j++) {
+      buf[j + offset] = current_value++;
+    }
+    scoped_ptr<FakeFileStreamReader> reader(new FakeFileStreamReader(
+        std::string(buf + offset, kItemSize), kItemSize + offset));
+    if (i % 4 != 0) {
+      reader->DoAsync(message_loop_.task_runner().get());
+    }
+    FilePath path = kPathBase.Append(
+        FilePath::FromUTF8Unsafe(base::StringPrintf("%d", current_value)));
+    ExpectLocalFileCall(path, kTime, offset, reader.release());
+  }
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  CheckSizeNotCalculatedYet(calculated_size);
+  message_loop_.RunUntilIdle();
+  CheckSizeCalculatedAsynchronously(kTotalSize, calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kBufferSize));
+
+  current_value = 0;
+  for (size_t i = 0; i < kTotalSize / kBufferSize; i++) {
+    int bytes_read = 0;
+    int async_bytes_read = 0;
+    EXPECT_EQ(BlobReader::Status::IO_PENDING,
+              reader_->Read(buffer.get(), kBufferSize, &bytes_read,
+                            base::Bind(&SetValue<int>, &async_bytes_read)));
+    message_loop_.RunUntilIdle();
+    EXPECT_EQ(net::OK, reader_->net_error());
+    EXPECT_EQ(0, bytes_read);
+    EXPECT_EQ(kBufferSize, static_cast<size_t>(async_bytes_read));
+    for (size_t j = 0; j < kBufferSize; j++) {
+      EXPECT_EQ(current_value, buffer->data()[j]);
+      current_value++;
+    }
+  }
+}
+
+TEST_F(BlobReaderTest, MixedContent) {
+  // Includes data, a file, and a disk cache entry.
+  scoped_ptr<disk_cache::Backend> cache =
+      CreateInMemoryDiskCache(message_loop_.task_runner());
+  ASSERT_TRUE(cache);
+
+  BlobDataBuilder b("uuid");
+  const std::string kData1("Hello ");
+  const std::string kData2("there. ");
+  const std::string kData3("This ");
+  const std::string kData4("is multi-content.");
+  const uint64_t kDataSize = 35;
+
+  const base::Time kTime = base::Time::Now();
+  const FilePath kData1Path = FilePath::FromUTF8Unsafe("/fake/file.txt");
+
+  disk_cache::ScopedEntryPtr entry3 =
+      CreateDiskCacheEntry(cache.get(), "test entry", kData3);
+
+  b.AppendFile(kData1Path, 0, kData1.size(), kTime);
+  b.AppendData(kData2);
+  b.AppendDiskCacheEntry(
+      scoped_refptr<BlobDataBuilder::DataHandle>(new EmptyDataHandle()),
+      entry3.get(), kTestDiskCacheStreamIndex);
+  b.AppendData(kData4);
+
+  this->InitializeReader(&b);
+
+  scoped_ptr<FakeFileStreamReader> reader(new FakeFileStreamReader(kData1));
+  reader->DoAsync(message_loop_.task_runner().get());
+  ExpectLocalFileCall(kData1Path, kTime, 0, reader.release());
+
+  int calculated_size = -1;
+  EXPECT_FALSE(IsReaderTotalSizeCalculated());
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  CheckSizeNotCalculatedYet(calculated_size);
+  message_loop_.RunUntilIdle();
+  CheckSizeCalculatedAsynchronously(kDataSize, calculated_size);
+
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(kDataSize);
+
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kDataSize, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(0, async_bytes_read);
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::OK, reader_->net_error());
+  EXPECT_EQ(0, bytes_read);
+  EXPECT_EQ(kDataSize, static_cast<size_t>(async_bytes_read));
+  EXPECT_EQ(0, memcmp(buffer->data(), "Hello there. This is multi-content.",
+                      kDataSize));
+}
+
+TEST_F(BlobReaderTest, StateErrors) {
+  // Test common variables
+  int bytes_read = -1;
+  int async_bytes_read = -1;
+  int calculated_size = -1;
+  const std::string kData("Hello!!!");
+
+  // Case: Blob handle is a nullptr.
+  InitializeReader(nullptr);
+  EXPECT_EQ(
+      BlobReader::Status::NET_ERROR,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+  EXPECT_EQ(BlobReader::Status::NET_ERROR, reader_->SetReadRange(0, 10));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(10);
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->Read(buffer.get(), 10, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+
+  // Case: Not calling CalculateSize before SetReadRange.
+  BlobDataBuilder builder1("uuid1");
+  builder1.AppendData(kData);
+  InitializeReader(&builder1);
+  EXPECT_EQ(BlobReader::Status::NET_ERROR, reader_->SetReadRange(0, 10));
+  EXPECT_EQ(net::ERR_FAILED, reader_->net_error());
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->Read(buffer.get(), 10, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::ERR_FAILED, reader_->net_error());
+  EXPECT_EQ(0, bytes_read);
+
+  // Case: Not calling CalculateSize before Read.
+  BlobDataBuilder builder2("uuid2");
+  builder2.AppendData(kData);
+  InitializeReader(&builder2);
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->Read(buffer.get(), 10, &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::ERR_FAILED, reader_->net_error());
+  EXPECT_EQ(0, bytes_read);
+}
+
+TEST_F(BlobReaderTest, FileErrorsSync) {
+  int calculated_size = -1;
+  const FilePath kPath = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+
+  // Case: Error on length query.
+  BlobDataBuilder builder1("uuid1");
+  builder1.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&builder1);
+  FakeFileStreamReader* reader = new FakeFileStreamReader(kData);
+  reader->ReturnError(net::ERR_FILE_NOT_FOUND);
+  ExpectLocalFileCall(kPath, kTime, 0, reader);
+
+  EXPECT_EQ(
+      BlobReader::Status::NET_ERROR,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+
+  // Case: Error on read.
+  BlobDataBuilder builder2("uuid2");
+  builder2.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&builder2);
+  reader = new FakeFileStreamReader(kData);
+  ExpectLocalFileCall(kPath, kTime, 0, reader);
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  reader->ReturnError(net::ERR_FILE_NOT_FOUND);
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+}
+
+TEST_F(BlobReaderTest, FileErrorsAsync) {
+  int calculated_size = -1;
+  const FilePath kPath = FilePath::FromUTF8Unsafe("/fake/file.txt");
+  const std::string kData = "FileData!!!";
+  const base::Time kTime = base::Time::Now();
+
+  // Case: Error on length query.
+  BlobDataBuilder builder1("uuid1");
+  builder1.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&builder1);
+  FakeFileStreamReader* reader = new FakeFileStreamReader(kData);
+  reader->DoAsync(message_loop_.task_runner().get());
+  reader->ReturnError(net::ERR_FILE_NOT_FOUND);
+  ExpectLocalFileCall(kPath, kTime, 0, reader);
+
+  EXPECT_EQ(
+      BlobReader::Status::IO_PENDING,
+      reader_->CalculateSize(base::Bind(&SetValue<int>, &calculated_size)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, calculated_size);
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+
+  // Case: Error on read.
+  BlobDataBuilder builder2("uuid2");
+  builder2.AppendFile(kPath, 0, kData.size(), kTime);
+  this->InitializeReader(&builder2);
+  reader = new FakeFileStreamReader(kData);
+  ExpectLocalFileCall(kPath, kTime, 0, reader);
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  reader->ReturnError(net::ERR_FILE_NOT_FOUND);
+  reader->DoAsync(message_loop_.task_runner().get());
+
+  scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(kData.size()));
+  int bytes_read = 0;
+  int async_bytes_read = 0;
+  EXPECT_EQ(BlobReader::Status::IO_PENDING,
+            reader_->Read(buffer.get(), kData.size(), &bytes_read,
+                          base::Bind(&SetValue<int>, &async_bytes_read)));
+  EXPECT_EQ(net::OK, reader_->net_error());
+  message_loop_.RunUntilIdle();
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, async_bytes_read);
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+}
+
+TEST_F(BlobReaderTest, RangeError) {
+  const std::string kData("Hello!!!");
+  const size_t kDataSize = 8ul;
+  const uint64_t kReadLength = 4ull;
+
+  // Case: offset too high.
+  BlobDataBuilder b("uuid1");
+  b.AppendData(kData);
+  this->InitializeReader(&b);
+  int calculated_size = -1;
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  scoped_refptr<net::IOBuffer> buffer = CreateBuffer(kDataSize);
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->SetReadRange(kDataSize + 1, kReadLength));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+
+  // Case: length too long.
+  BlobDataBuilder b2("uuid2");
+  b2.AppendData(kData);
+  this->InitializeReader(&b2);
+  calculated_size = -1;
+  EXPECT_EQ(BlobReader::Status::DONE, reader_->CalculateSize(base::Bind(
+                                          &SetValue<int>, &calculated_size)));
+  buffer = CreateBuffer(kDataSize + 1);
+  EXPECT_EQ(BlobReader::Status::NET_ERROR,
+            reader_->SetReadRange(0, kDataSize + 1));
+  EXPECT_EQ(net::ERR_FILE_NOT_FOUND, reader_->net_error());
+}
+
+}  // namespace
+}  // namespace storage