Added MojoNewWait and MojoNewWaitMany, along with unit tests.

mojo/edk/embedder/embedder_unittest.cc

Index: mojo/edk/embedder/embedder_unittest.cc
diff --git a/mojo/edk/embedder/embedder_unittest.cc b/mojo/edk/embedder/embedder_unittest.cc
index b138a2d67d6cf21284c88739db6463b7fd98b773..087d024208ee84217f17cb67fa46a08d83f4122e 100644
--- a/mojo/edk/embedder/embedder_unittest.cc
+++ b/mojo/edk/embedder/embedder_unittest.cc
@@ -497,3 +497,533 @@ MOJO_MULTIPROCESS_TEST_CHILD_TEST(MultiprocessChannelsClient) {
 }  // namespace
 }  // namespace embedder
 }  // namespace mojo
+
+// TODO(jimbe) Remove code above and rename calls to wait below.
+
+namespace mojo {
+namespace embedder {
+namespace new_wait {
+
+const MojoHandleSignals MOJO_HANDLE_SIGNAL_READWRITABLE =
+    MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_WRITABLE;
+
+const MojoHandleSignals MOJO_HANDLE_SIGNAL_ALL = MOJO_HANDLE_SIGNAL_READABLE |
+                                                 MOJO_HANDLE_SIGNAL_WRITABLE |
+                                                 MOJO_HANDLE_SIGNAL_PEER_CLOSED;
+
+class ScopedTestChannel {
+ public:
+  // Creates a channel that lives on a given I/O thread (determined by the given
+  // |TaskRunner|) attached to the given |platform_handle|. After construction,
+  // |bootstrap_message_pipe()| gives the Mojo handle for the bootstrap message
+  // pipe on this channel; it is up to the caller to close this handle.
+  // Note: The I/O thread must outlive this object (and its message loop must
+  // continue pumping messages while this object is alive).
+  ScopedTestChannel(scoped_refptr<base::TaskRunner> io_thread_task_runner,
+                    ScopedPlatformHandle platform_handle)
+      : io_thread_task_runner_(io_thread_task_runner),
+        bootstrap_message_pipe_(MOJO_HANDLE_INVALID),
+        did_create_channel_event_(true, false),
+        channel_info_(nullptr) {
+    bootstrap_message_pipe_ =
+        CreateChannel(platform_handle.Pass(), io_thread_task_runner_,
+                      base::Bind(&ScopedTestChannel::DidCreateChannel,
+                                 base::Unretained(this)),
+                      nullptr)
+            .release()
+            .value();
+    CHECK_NE(bootstrap_message_pipe_, MOJO_HANDLE_INVALID);
+  }
+
+  // Destructor: Shuts down the channel. (As noted above, for this to happen,
+  // the I/O thread must be alive and pumping messages.)
+  ~ScopedTestChannel() { DestroyChannel(channel_info_); }
+
+  // Waits for channel creation to be completed.
+  void WaitForChannelCreationCompletion() { did_create_channel_event_.Wait(); }
+
+  MojoHandle bootstrap_message_pipe() const { return bootstrap_message_pipe_; }
+
+  // Call only after |WaitForChannelCreationCompletion()|. Use only to check
+  // that it's not null.
+  const ChannelInfo* channel_info() const { return channel_info_; }
+
+ private:
+  void DidCreateChannel(ChannelInfo* channel_info) {
+    CHECK(channel_info);
+    CHECK(!channel_info_);
+    channel_info_ = channel_info;
+    did_create_channel_event_.Signal();
+  }
+
+  scoped_refptr<base::TaskRunner> io_thread_task_runner_;
+
+  // Valid from creation until whenever it gets closed (by the "owner" of this
+  // object).
+  // Note: We don't want use the C++ wrappers here, since we want to test the
+  // API at the lowest level.
+  MojoHandle bootstrap_message_pipe_;
+
+  // Set after channel creation has been completed (i.e., the callback to
+  // |CreateChannel()| has been called).
+  base::WaitableEvent did_create_channel_event_;
+
+  // Valid after channel creation completion until destruction.
+  ChannelInfo* channel_info_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedTestChannel);
+};
+
+class NewEmbedderTest : public testing::Test {
+ public:
+  NewEmbedderTest() : test_io_thread_(base::TestIOThread::kAutoStart) {}
+  ~NewEmbedderTest() override {}
+
+ protected:
+  base::TestIOThread* test_io_thread() { return &test_io_thread_; }
+
+ private:
+  base::TestIOThread test_io_thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(NewEmbedderTest);
+};
+
+TEST_F(NewEmbedderTest, ChannelsBasic) {
+  mojo::embedder::test::InitWithSimplePlatformSupport();
+
+  {
+    PlatformChannelPair channel_pair;
+    ScopedTestChannel server_channel(test_io_thread()->task_runner(),
+                                     channel_pair.PassServerHandle());
+    MojoHandle server_mp = server_channel.bootstrap_message_pipe();
+    EXPECT_NE(server_mp, MOJO_HANDLE_INVALID);
+    ScopedTestChannel client_channel(test_io_thread()->task_runner(),
+                                     channel_pair.PassClientHandle());
+    MojoHandle client_mp = client_channel.bootstrap_message_pipe();
+    EXPECT_NE(client_mp, MOJO_HANDLE_INVALID);
+
+    // We can write to a message pipe handle immediately.
+    const char kHello[] = "hello";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(server_mp, kHello,
+                               static_cast<uint32_t>(sizeof(kHello)), nullptr,
+                               0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Now wait for the other side to become readable.
+    MojoHandleSignalsState state;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoNewWait(client_mp, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    char buffer[1000] = {};
+    uint32_t num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(client_mp, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    EXPECT_EQ(sizeof(kHello), num_bytes);
+    EXPECT_STREQ(kHello, buffer);
+
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(server_mp));
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(client_mp));
+
+    // By this point, these waits should basically be no-ops (since we've waited
+    // for the client message pipe to become readable, which implies that both
+    // the server and client channels were completely created).
+    server_channel.WaitForChannelCreationCompletion();
+    client_channel.WaitForChannelCreationCompletion();
+    EXPECT_TRUE(server_channel.channel_info());
+    EXPECT_TRUE(client_channel.channel_info());
+  }
+
+  EXPECT_TRUE(test::Shutdown());
+}
+
+TEST_F(NewEmbedderTest, ChannelsHandlePassing) {
+  mojo::embedder::test::InitWithSimplePlatformSupport();
+
+  {
+    PlatformChannelPair channel_pair;
+    ScopedTestChannel server_channel(test_io_thread()->task_runner(),
+                                     channel_pair.PassServerHandle());
+    MojoHandle server_mp = server_channel.bootstrap_message_pipe();
+    EXPECT_NE(server_mp, MOJO_HANDLE_INVALID);
+    ScopedTestChannel client_channel(test_io_thread()->task_runner(),
+                                     channel_pair.PassClientHandle());
+    MojoHandle client_mp = client_channel.bootstrap_message_pipe();
+    EXPECT_NE(client_mp, MOJO_HANDLE_INVALID);
+
+    MojoHandle h0, h1;
+    EXPECT_EQ(MOJO_RESULT_OK, MojoCreateMessagePipe(nullptr, &h0, &h1));
+
+    // Write a message to |h0| (attaching nothing).
+    const char kHello[] = "hello";
+    EXPECT_EQ(
+        MOJO_RESULT_OK,
+        MojoWriteMessage(h0, kHello, static_cast<uint32_t>(sizeof(kHello)),
+                         nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Write one message to |server_mp|, attaching |h1|.
+    const char kWorld[] = "world!!!";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(server_mp, kWorld,
+                               static_cast<uint32_t>(sizeof(kWorld)), &h1, 1,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+    h1 = MOJO_HANDLE_INVALID;
+
+    // Write another message to |h0|.
+    const char kFoo[] = "foo";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h0, kFoo, static_cast<uint32_t>(sizeof(kFoo)),
+                               nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Wait for |client_mp| to become readable.
+    MojoHandleSignalsState state;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoNewWait(client_mp, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    // Read a message from |client_mp|.
+    char buffer[1000] = {};
+    uint32_t num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    MojoHandle handles[10] = {};
+    uint32_t num_handles = arraysize(handles);
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(client_mp, buffer, &num_bytes, handles,
+                              &num_handles, MOJO_READ_MESSAGE_FLAG_NONE));
+    EXPECT_EQ(sizeof(kWorld), num_bytes);
+    EXPECT_STREQ(kWorld, buffer);
+    EXPECT_EQ(1u, num_handles);
+    EXPECT_NE(handles[0], MOJO_HANDLE_INVALID);
+    h1 = handles[0];
+
+    // Wait for |h1| to become readable.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(h1, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    // Read a message from |h1|.
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    memset(handles, 0, sizeof(handles));
+    num_handles = arraysize(handles);
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(h1, buffer, &num_bytes, handles, &num_handles,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    EXPECT_EQ(sizeof(kHello), num_bytes);
+    EXPECT_STREQ(kHello, buffer);
+    EXPECT_EQ(0u, num_handles);
+
+    // Wait for |h1| to become readable (again).
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(h1, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    // Read the second message from |h1|.
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(h1, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    EXPECT_EQ(sizeof(kFoo), num_bytes);
+    EXPECT_STREQ(kFoo, buffer);
+
+    // Write a message to |h1|.
+    const char kBarBaz[] = "barbaz";
+    EXPECT_EQ(
+        MOJO_RESULT_OK,
+        MojoWriteMessage(h1, kBarBaz, static_cast<uint32_t>(sizeof(kBarBaz)),
+                         nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Wait for |h0| to become readable.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(h0, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    // Read a message from |h0|.
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(h0, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    EXPECT_EQ(sizeof(kBarBaz), num_bytes);
+    EXPECT_STREQ(kBarBaz, buffer);
+
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(server_mp));
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(client_mp));
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h0));
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
+
+    server_channel.WaitForChannelCreationCompletion();
+    client_channel.WaitForChannelCreationCompletion();
+    EXPECT_TRUE(server_channel.channel_info());
+    EXPECT_TRUE(client_channel.channel_info());
+  }
+
+  EXPECT_TRUE(test::Shutdown());
+}
+
+// The sequence of messages sent is:
+//       server_mp   client_mp   mp0         mp1         mp2         mp3
+//   1.  "hello"
+//   2.              "world!"
+//   3.                          "FOO"
+//   4.  "Bar"+mp1
+//   5.  (close)
+//   6.              (close)
+//   7.                                                              "baz"
+//   8.                                                              (closed)
+//   9.                                      "quux"+mp2
+//  10.                          (close)
+//  11.                                      (wait/cl.)
+//  12.                                                  (wait/cl.)
+TEST_F(NewEmbedderTest, MultiprocessChannels) {
+  mojo::embedder::test::InitWithSimplePlatformSupport();
+  mojo::test::MultiprocessTestHelper multiprocess_test_helper;
+  multiprocess_test_helper.StartChild("MultiprocessChannelsClient");
+
+  {
+    ScopedTestChannel server_channel(
+        test_io_thread()->task_runner(),
+        multiprocess_test_helper.server_platform_handle.Pass());
+    MojoHandle server_mp = server_channel.bootstrap_message_pipe();
+    EXPECT_NE(server_mp, MOJO_HANDLE_INVALID);
+    server_channel.WaitForChannelCreationCompletion();
+    EXPECT_TRUE(server_channel.channel_info());
+
+    // 1. Write a message to |server_mp| (attaching nothing).
+    const char kHello[] = "hello";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(server_mp, kHello,
+                               static_cast<uint32_t>(sizeof(kHello)), nullptr,
+                               0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // TODO(vtl): If the scope were ended immediately here (maybe after closing
+    // |server_mp|), we die with a fatal error in |Channel::HandleLocalError()|.
+
+    // 2. Read a message from |server_mp|.
+    MojoHandleSignalsState state;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoNewWait(server_mp, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    char buffer[1000] = {};
+    uint32_t num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(server_mp, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kWorld[] = "world!";
+    EXPECT_EQ(sizeof(kWorld), num_bytes);
+    EXPECT_STREQ(kWorld, buffer);
+
+    // Create a new message pipe (endpoints |mp0| and |mp1|).
+    MojoHandle mp0, mp1;
+    EXPECT_EQ(MOJO_RESULT_OK, MojoCreateMessagePipe(nullptr, &mp0, &mp1));
+
+    // 3. Write something to |mp0|.
+    const char kFoo[] = "FOO";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp0, kFoo, static_cast<uint32_t>(sizeof(kFoo)),
+                               nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // 4. Write a message to |server_mp|, attaching |mp1|.
+    const char kBar[] = "Bar";
+    EXPECT_EQ(
+        MOJO_RESULT_OK,
+        MojoWriteMessage(server_mp, kBar, static_cast<uint32_t>(sizeof(kBar)),
+                         &mp1, 1, MOJO_WRITE_MESSAGE_FLAG_NONE));
+    mp1 = MOJO_HANDLE_INVALID;
+
+    // 5. Close |server_mp|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(server_mp));
+
+    // 9. Read a message from |mp0|, which should have |mp2| attached.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(mp0, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    MojoHandle mp2 = MOJO_HANDLE_INVALID;
+    uint32_t num_handles = 1;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(mp0, buffer, &num_bytes, &mp2, &num_handles,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kQuux[] = "quux";
+    EXPECT_EQ(sizeof(kQuux), num_bytes);
+    EXPECT_STREQ(kQuux, buffer);
+    EXPECT_EQ(1u, num_handles);
+    EXPECT_NE(mp2, MOJO_HANDLE_INVALID);
+
+    // 7. Read a message from |mp2|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(mp2, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+              state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+              state.satisfiable_signals);
+
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(mp2, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kBaz[] = "baz";
+    EXPECT_EQ(sizeof(kBaz), num_bytes);
+    EXPECT_STREQ(kBaz, buffer);
+
+    // 10. Close |mp0|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(mp0));
+
+// 12. Wait on |mp2| (which should eventually fail) and then close it.
+// TODO(vtl): crbug.com/351768
+#if 0
+    EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
+              MojoNewWait(mp2, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE,
+                       &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_NONE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_NONE, state.satisfiable_signals);
+#endif
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(mp2));
+  }
+
+  EXPECT_TRUE(multiprocess_test_helper.WaitForChildTestShutdown());
+  EXPECT_TRUE(test::Shutdown());
+}
+
+MOJO_MULTIPROCESS_TEST_CHILD_TEST(MultiprocessChannelsClient) {
+  ScopedPlatformHandle client_platform_handle =
+      mojo::test::MultiprocessTestHelper::client_platform_handle.Pass();
+  EXPECT_TRUE(client_platform_handle.is_valid());
+
+  base::TestIOThread test_io_thread(base::TestIOThread::kAutoStart);
+  mojo::embedder::test::InitWithSimplePlatformSupport();
+
+  {
+    ScopedTestChannel client_channel(test_io_thread.task_runner(),
+                                     client_platform_handle.Pass());
+    MojoHandle client_mp = client_channel.bootstrap_message_pipe();
+    EXPECT_NE(client_mp, MOJO_HANDLE_INVALID);
+    client_channel.WaitForChannelCreationCompletion();
+    CHECK(client_channel.channel_info() != nullptr);
+
+    // 1. Read the first message from |client_mp|.
+    MojoHandleSignalsState state;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoNewWait(client_mp, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    char buffer[1000] = {};
+    uint32_t num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(client_mp, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kHello[] = "hello";
+    EXPECT_EQ(sizeof(kHello), num_bytes);
+    EXPECT_STREQ(kHello, buffer);
+
+    // 2. Write a message to |client_mp| (attaching nothing).
+    const char kWorld[] = "world!";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(client_mp, kWorld,
+                               static_cast<uint32_t>(sizeof(kWorld)), nullptr,
+                               0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // 4. Read a message from |client_mp|, which should have |mp1| attached.
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoNewWait(client_mp, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    // The other end of the handle may or may not be closed at this point, so we
+    // can't test MOJO_HANDLE_SIGNAL_WRITABLE or MOJO_HANDLE_SIGNAL_PEER_CLOSED.
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE,
+              state.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READABLE,
+              state.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE);
+    // TODO(vtl): If the scope were to end here (and |client_mp| closed), we'd
+    // die (again due to |Channel::HandleLocalError()|).
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    MojoHandle mp1 = MOJO_HANDLE_INVALID;
+    uint32_t num_handles = 1;
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(client_mp, buffer, &num_bytes, &mp1, &num_handles,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kBar[] = "Bar";
+    EXPECT_EQ(sizeof(kBar), num_bytes);
+    EXPECT_STREQ(kBar, buffer);
+    EXPECT_EQ(1u, num_handles);
+    EXPECT_NE(mp1, MOJO_HANDLE_INVALID);
+    // TODO(vtl): If the scope were to end here (and the two handles closed),
+    // we'd die due to |Channel::RunRemoteMessagePipeEndpoint()| not handling
+    // write errors (assuming the parent had closed the pipe).
+
+    // 6. Close |client_mp|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(client_mp));
+
+    // Create a new message pipe (endpoints |mp2| and |mp3|).
+    MojoHandle mp2, mp3;
+    EXPECT_EQ(MOJO_RESULT_OK, MojoCreateMessagePipe(nullptr, &mp2, &mp3));
+
+    // 7. Write a message to |mp3|.
+    const char kBaz[] = "baz";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp3, kBaz, static_cast<uint32_t>(sizeof(kBaz)),
+                               nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // 8. Close |mp3|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(mp3));
+
+    // 9. Write a message to |mp1|, attaching |mp2|.
+    const char kQuux[] = "quux";
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp1, kQuux, static_cast<uint32_t>(sizeof(kQuux)),
+                               &mp2, 1, MOJO_WRITE_MESSAGE_FLAG_NONE));
+    mp2 = MOJO_HANDLE_INVALID;
+
+    // 3. Read a message from |mp1|.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoNewWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
+                                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_READWRITABLE, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_ALL, state.satisfiable_signals);
+
+    memset(buffer, 0, sizeof(buffer));
+    num_bytes = static_cast<uint32_t>(sizeof(buffer));
+    EXPECT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(mp1, buffer, &num_bytes, nullptr, nullptr,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    const char kFoo[] = "FOO";
+    EXPECT_EQ(sizeof(kFoo), num_bytes);
+    EXPECT_STREQ(kFoo, buffer);
+
+    // 11. Wait on |mp1| (which should eventually fail) and then close it.
+    EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
+              MojoNewWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
+                          MOJO_DEADLINE_INDEFINITE, &state));
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, state.satisfied_signals);
+    EXPECT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, state.satisfiable_signals);
+    EXPECT_EQ(MOJO_RESULT_OK, MojoClose(mp1));
+  }
+
+  EXPECT_TRUE(test::Shutdown());
+}
+
+// TODO(vtl): Test immediate write & close.
+// TODO(vtl): Test broken-connection cases.
+
+}  // namespace
+}  // namespace embedder
+}  // namespace mojo
+
+// End TODO(jimbe)