Creation of ByteStream class.

content/browser/download/byte_stream_unittest.cc

+// Copyright (c) 2012 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/browser/download/byte_stream.h"
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/location.h"
+#include "base/memory/ref_counted.h"
+#include "base/message_loop.h"
+#include "base/task_runner.h"
+#include "net/base/io_buffer.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using ::testing::_;
+using ::testing::Return;
+using ::testing::SaveArg;
+using ::testing::StrictMock;
+
+namespace tracked_objects {
+class Location;
+}
+
+namespace {
+
+class MockTaskRunner : public base::SequencedTaskRunner {
+ public:
+  MockTaskRunner();
+
+  // TaskRunner functions.
+  MOCK_METHOD3(PostDelayedTask, bool(const tracked_objects::Location&,
+                                     const base::Closure&, int64));
+  MOCK_METHOD3(PostDelayedTask, bool(const tracked_objects::Location&,
+                                     const base::Closure&, base::TimeDelta));
+
+  MOCK_METHOD3(PostNonNestableDelayedTask, bool(
+      const tracked_objects::Location&,
+      const base::Closure&,
+      int64 delay_ms));
+
+  MOCK_METHOD3(PostNonNestableDelayedTask, bool(
+      const tracked_objects::Location&,
+      const base::Closure&,
+      base::TimeDelta));
+
+  MOCK_CONST_METHOD0(RunsTasksOnCurrentThread, bool());
+
+ protected:
+  ~MockTaskRunner();
+};
+
+MockTaskRunner::MockTaskRunner() { }
+
+MockTaskRunner::~MockTaskRunner() { }
+
+static int null_callback_call_count = 0;
+static int alt_callback_call_count = 0;
+
+void NullCallback() {
+  null_callback_call_count++;
+}
+
+void AltCallback() {
+  alt_callback_call_count++;
+}
+
+}  // namespace
+
+class ByteStreamTest : public testing::Test {
+ public:
+  // Create a new IO buffer of the given |buffer_size|, with contents
+  // dependent on the |seed_key|.  The |seed_key| is also used for comparing
+  // pointers between NewIOBuffer and ValidateIOBuffer; do not re-use any
+  // |seed_key| value within a single test.
+  scoped_refptr<net::IOBuffer> NewIOBuffer(size_t buffer_size, int seed_key) {
+    scoped_refptr<net::IOBuffer> buffer(new net::IOBuffer(buffer_size));
+    char *bufferp = buffer->data();
+    for (size_t i = 0; i < buffer_size; i++)
+      bufferp[i] = (i + seed_key) % (1 << sizeof(char));
+    DCHECK(pointer_map_.find(seed_key) == pointer_map_.end());
+    DCHECK(length_map_.find(seed_key) == length_map_.end());
+    pointer_map_[seed_key] = bufferp;
+    length_map_[seed_key] = buffer_size;
+    return buffer;
+  }
+
+  // Create an IOBuffer of the appropriate size and add it to the
+  // ByteStream, returning the result of the ByteStream::AddData.
+  // Separate function to avoid duplication of buffer_size in test
+  // calls.
+  bool AddData(content::ByteStreamInput* byte_stream_input,
+               int seed_key, size_t buffer_size) {
+    return byte_stream_input->AddData(NewIOBuffer(buffer_size, seed_key),
+                                      buffer_size);
+  }
+
+  // Validate that we have the IOBuffer we expect.  This IOBuffer must
+  // have been created through NewIOBuffer with the given |buffer_size|
+  // and |seed_key|.
+  bool ValidateIOBuffer(scoped_refptr<net::IOBuffer> buffer, int seed_key,
+                        size_t buffer_size) {
+    char *bufferp = buffer->data();
+    EXPECT_TRUE(pointer_map_.find(seed_key) != pointer_map_.end());
+    if (pointer_map_.find(seed_key) == pointer_map_.end())
+      return false;
+    EXPECT_EQ(bufferp, pointer_map_[seed_key]);
+    EXPECT_TRUE(length_map_.find(seed_key) != length_map_.end());
+    if (length_map_.find(seed_key) == length_map_.end())
+      return false;
+    EXPECT_EQ(buffer_size, length_map_[seed_key]);
+    for (size_t i = 0; i < buffer_size; i++) {
+      EXPECT_EQ(static_cast<int>((i + seed_key) % (1 << sizeof(char))),
+                bufferp[i]);
+      if (static_cast<int>((i + seed_key) % (1 << sizeof(char))) != bufferp[i])
+        return false;
+    }
+    return true;
+  }
+
+ protected:
+  MessageLoop message_loop_;
+ private:
+  std::map<int, char*> pointer_map_;
+  std::map<int, size_t> length_map_;
+};
+
+// Confirm that filling and emptying the pipe works properly, and that
+// we get full triggers when we expect.
+TEST_F(ByteStreamTest, PushBack) {
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      3 * 1024);
+
+  // Push a series of IO buffers on; test pushback happening and
+  // that it's advisory.
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 1024));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 1024));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 2, 1024));
+  EXPECT_FALSE(AddData(byte_stream_input.get(), 3, 1));
+  EXPECT_FALSE(AddData(byte_stream_input.get(), 4, 1024));
+  EXPECT_EQ(0u, byte_stream_output->BytesRead());
+  EXPECT_EQ(0u, byte_stream_output->BuffersRead());
+  // Flush
+  byte_stream_input->SourceComplete(content::DOWNLOAD_INTERRUPT_REASON_NONE);
+  message_loop_.RunAllPending();
+
+  // Pull the IO buffers out; do we get the same buffers and do they
+  // have the same contents?
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  EXPECT_EQ(1024u, byte_stream_output->BytesRead());
+  EXPECT_EQ(1u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 1, output_length));
+  EXPECT_EQ(2048u, byte_stream_output->BytesRead());
+  EXPECT_EQ(2u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 2, output_length));
+  EXPECT_EQ(3072u, byte_stream_output->BytesRead());
+  EXPECT_EQ(3u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 3, output_length));
+  EXPECT_EQ(3073u, byte_stream_output->BytesRead());
+  EXPECT_EQ(4u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 4, output_length));
+  EXPECT_EQ(4097u, byte_stream_output->BytesRead());
+  EXPECT_EQ(5u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_COMPLETE,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+}
+
+// Same as above, only use knowledge of the internals to confirm
+// that we're getting pushback even when data's split across the two
+// objects
+TEST_F(ByteStreamTest, PushBackSplit) {
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      9 * 1024);
+
+  // Push a series of IO buffers on; test pushback happening and
+  // that it's advisory.
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 1024));
+  message_loop_.RunAllPending();
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 1024));
+  message_loop_.RunAllPending();
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 2, 1024));
+  message_loop_.RunAllPending();
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 3, 1024));
+  message_loop_.RunAllPending();
+  EXPECT_FALSE(AddData(byte_stream_input.get(), 4, 6 * 1024));
+  message_loop_.RunAllPending();
+  EXPECT_EQ(0u, byte_stream_output->BytesRead());
+  EXPECT_EQ(0u, byte_stream_output->BuffersRead());
+
+  // Pull the IO buffers out; do we get the same buffers and do they
+  // have the same contents?
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  EXPECT_EQ(1024u, byte_stream_output->BytesRead());
+  EXPECT_EQ(1u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 1, output_length));
+  EXPECT_EQ(2048u, byte_stream_output->BytesRead());
+  EXPECT_EQ(2u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 2, output_length));
+  EXPECT_EQ(3072u, byte_stream_output->BytesRead());
+  EXPECT_EQ(3u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 3, output_length));
+  EXPECT_EQ(4096u, byte_stream_output->BytesRead());
+  EXPECT_EQ(4u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 4, output_length));
+  EXPECT_EQ(10240u, byte_stream_output->BytesRead());
+  EXPECT_EQ(5u, byte_stream_output->BuffersRead());
+
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+}
+
+// Confirm that a SourceComplete() notification transmits in-order
+// with data on the pipe.
+TEST_F(ByteStreamTest, CompleteTransmits) {
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+
+  // Empty stream, non-error case.
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      3 * 1024);
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  byte_stream_input->SourceComplete(content::DOWNLOAD_INTERRUPT_REASON_NONE);
+  message_loop_.RunAllPending();
+  ASSERT_EQ(content::ByteStreamOutput::STREAM_COMPLETE,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(content::DOWNLOAD_INTERRUPT_REASON_NONE,
+            byte_stream_output->GetSourceResult());
+
+  // Non-empty stream, non-error case.
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      3 * 1024);
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 1024));
+  byte_stream_input->SourceComplete(content::DOWNLOAD_INTERRUPT_REASON_NONE);
+  message_loop_.RunAllPending();
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  ASSERT_EQ(content::ByteStreamOutput::STREAM_COMPLETE,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(content::DOWNLOAD_INTERRUPT_REASON_NONE,
+            byte_stream_output->GetSourceResult());
+
+  // Empty stream, non-error case.
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      3 * 1024);
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  byte_stream_input->SourceComplete(
+      content::DOWNLOAD_INTERRUPT_REASON_NETWORK_DISCONNECTED);
+  message_loop_.RunAllPending();
+  ASSERT_EQ(content::ByteStreamOutput::STREAM_COMPLETE,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(content::DOWNLOAD_INTERRUPT_REASON_NETWORK_DISCONNECTED,
+            byte_stream_output->GetSourceResult());
+
+  // Non-empty stream, non-error case.
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), message_loop_.message_loop_proxy(),
+      3 * 1024);
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 1024));
+  byte_stream_input->SourceComplete(
+      content::DOWNLOAD_INTERRUPT_REASON_NETWORK_DISCONNECTED);
+  message_loop_.RunAllPending();
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 1, output_length));
+  ASSERT_EQ(content::ByteStreamOutput::STREAM_COMPLETE,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(content::DOWNLOAD_INTERRUPT_REASON_NETWORK_DISCONNECTED,
+            byte_stream_output->GetSourceResult());
+}
+
+// Confirm that callbacks on the sink side are triggered when they should be.
+TEST_F(ByteStreamTest, SinkCallback) {
+  scoped_refptr<MockTaskRunner> task_runner(new StrictMock<MockTaskRunner>());
+  int null_callback_call_count_start = 0;
+
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), task_runner,
+      10000);
+
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  base::Closure intermediate_callback;
+
+  // Note that the specifics of when the callbacks are called with regard
+  // to how much data is pushed onto the pipe is not (currently) part
+  // of the interface contract.  If it becomes part of the contract, the
+  // tests below should get much more precise.
+
+  // Confirm callback called when you add more than 33% of the buffer.
+
+  // Setup callback
+  byte_stream_output->RegisterCallback(base::Bind(NullCallback));
+  null_callback_call_count_start = null_callback_call_count;
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+  EXPECT_EQ(0u, byte_stream_output->NumSinkCallbacks());
+
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 4000));
+  message_loop_.RunAllPending();
+
+  // Check callback results match expectations.
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  intermediate_callback.Run();
+  EXPECT_EQ(null_callback_call_count_start+1, null_callback_call_count);
+  EXPECT_EQ(1u, byte_stream_output->NumSinkCallbacks());
+
+  // Check data and stream state.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+
+  // Confirm callback *isn't* called at less than 33%
+  null_callback_call_count_start = null_callback_call_count;
+  EXPECT_EQ(1u, byte_stream_output->NumSinkCallbacks());
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 3000));
+  message_loop_.RunAllPending();
+  EXPECT_EQ(1u, byte_stream_output->NumSinkCallbacks());
+
+  // This reflects an implementation artifact that data goes with callbacks,
+  // which should not be considered part of the interface guarantee.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+}
+
+// Confirm that callbacks on the source side are triggered when they should
+// be.
+TEST_F(ByteStreamTest, SourceCallback) {
+  scoped_refptr<MockTaskRunner> task_runner(new StrictMock<MockTaskRunner>());
+  int null_callback_call_count_start = 0;
+
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      task_runner, message_loop_.message_loop_proxy(),
+      10000);
+
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  base::Closure intermediate_callback;
+
+  // Note that the specifics of when the callbacks are called with regard
+  // to how much data is pulled from the pipe is not (currently) part
+  // of the interface contract.  If it becomes part of the contract, the
+  // tests below should get much more precise.
+
+  // Confirm callback called when about 33% space available, and not
+  // at other transitions.
+
+  // Setup expectations and add data.
+  byte_stream_input->RegisterCallback(base::Bind(NullCallback));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 2000));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 2001));
+  EXPECT_FALSE(AddData(byte_stream_input.get(), 2, 6000));
+  null_callback_call_count_start = null_callback_call_count;
+
+  // Allow bytes to transition (needed for message passing implementation),
+  // and get and validate the data.
+  message_loop_.RunAllPending();
+  EXPECT_EQ(0u, byte_stream_output->NumSourceCallbacks());
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+
+  // Setup expectations.
+  EXPECT_EQ(0u, byte_stream_output->NumSourceCallbacks());
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+
+  // Grab data, triggering callback.  Recorded on dispatch, but doesn't
+  // happen because it's caught by the mock.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(1u, byte_stream_output->NumSourceCallbacks());
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 1, output_length));
+
+  // Confirm that the callback passed to the mock does what we expect.
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  intermediate_callback.Run();
+  EXPECT_EQ(null_callback_call_count_start+1, null_callback_call_count);
+
+  // Same drill with final buffer.
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(2u, byte_stream_output->NumSourceCallbacks());
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 2, output_length));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(null_callback_call_count_start+1, null_callback_call_count);
+}
+
+// Confirm that racing a change to a sink callback with a post results
+// in the new callback being called.
+TEST_F(ByteStreamTest, SinkInterrupt) {
+  scoped_refptr<MockTaskRunner> task_runner(new StrictMock<MockTaskRunner>());
+  int null_callback_call_count_start = 0;
+  int alt_callback_call_count_start = 0;
+
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      message_loop_.message_loop_proxy(), task_runner,
+      10000);
+
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  base::Closure intermediate_callback;
+
+  // Setup expectations and record initial state.
+  byte_stream_output->RegisterCallback(base::Bind(NullCallback));
+  null_callback_call_count_start = null_callback_call_count;
+  alt_callback_call_count_start = alt_callback_call_count;
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+  EXPECT_EQ(0u, byte_stream_output->NumSinkCallbacks());
+
+  // Add data, and pass it across.
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 4000));
+  message_loop_.RunAllPending();
+
+  // The task runner should have been hit, but the callback count
+  // isn't changed until we actually run the callback.
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+
+  // If we change the callback now, the new one should be run
+  // (simulates race with post task).
+  byte_stream_output->RegisterCallback(base::Bind(AltCallback));
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  EXPECT_EQ(alt_callback_call_count_start, alt_callback_call_count);
+  intermediate_callback.Run();
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  EXPECT_EQ(alt_callback_call_count_start+1, alt_callback_call_count);
+  EXPECT_EQ(1u, byte_stream_output->NumSinkCallbacks());
+
+  // Final cleanup.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+
+}
+
+// Confirm that racing a change to a source callback with a post results
+// in the new callback being called.
+TEST_F(ByteStreamTest, SourceInterrupt) {
+  scoped_refptr<MockTaskRunner> task_runner(new StrictMock<MockTaskRunner>());
+  int null_callback_call_count_start = 0;
+  int alt_callback_call_count_start = 0;
+
+  scoped_ptr<content::ByteStreamInput> byte_stream_input;
+  scoped_ptr<content::ByteStreamOutput> byte_stream_output;
+  content::CreateByteStream(
+      &byte_stream_input, &byte_stream_output,
+      task_runner, message_loop_.message_loop_proxy(),
+      10000);
+
+  scoped_refptr<net::IOBuffer> output_io_buffer;
+  size_t output_length;
+  base::Closure intermediate_callback;
+
+  // Setup state for test and record initiali expectations
+  byte_stream_input->RegisterCallback(base::Bind(NullCallback));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 0, 2000));
+  EXPECT_TRUE(AddData(byte_stream_input.get(), 1, 2001));
+  EXPECT_FALSE(AddData(byte_stream_input.get(), 2, 6000));
+  null_callback_call_count_start = null_callback_call_count;
+  alt_callback_call_count_start = alt_callback_call_count;
+  message_loop_.RunAllPending();
+  EXPECT_EQ(0u, byte_stream_output->NumSourceCallbacks());
+
+  // Initial get should not trigger callback.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 0, output_length));
+  message_loop_.RunAllPending();
+  EXPECT_EQ(0u, byte_stream_output->NumSourceCallbacks());
+
+  // Setup expectations.
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+
+  // Second get *should* trigger callback.
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(1u, byte_stream_output->NumSourceCallbacks());
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 1, output_length));
+
+  // Which should do the right thing when it's run.
+  byte_stream_input->RegisterCallback(base::Bind(AltCallback));
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  EXPECT_EQ(alt_callback_call_count_start, alt_callback_call_count);
+  intermediate_callback.Run();
+  EXPECT_EQ(null_callback_call_count_start, null_callback_call_count);
+  EXPECT_EQ(alt_callback_call_count_start+1, alt_callback_call_count);
+
+  // Third get should also trigger callback.
+  EXPECT_CALL(*task_runner.get(), PostDelayedTask(_, _, 0))
+      .WillOnce(DoAll(SaveArg<1>(&intermediate_callback),
+                      Return(true)));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_HAS_DATA,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+  EXPECT_EQ(2u, byte_stream_output->NumSourceCallbacks());
+  ::testing::Mock::VerifyAndClearExpectations(task_runner.get());
+  EXPECT_TRUE(ValidateIOBuffer(output_io_buffer, 2, output_length));
+  EXPECT_EQ(content::ByteStreamOutput::STREAM_EMPTY,
+            byte_stream_output->GetData(&output_io_buffer, &output_length));
+}