Mojo: Generate bindings that make use of ScopedMessagePipeHandle.

R=abarth@chromium.org, davemoore@google.com, viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/97713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238592 0039d316-1c4b-4281-b951-d872f2087c98

41 files changed, 590 insertions, 182 deletions

diff --git a/mojo/apps/js/bindings/codec_unittests.js b/mojo/apps/js/bindings/codec_unittests.js
index d8d8ba0..4511033 100644
--- a/mojo/apps/js/bindings/codec_unittests.js
+++ b/mojo/apps/js/bindings/codec_unittests.js
@@ -76,13 +76,11 @@ define([
       foo.extra_bars[i].gamma = 3 * i;
     }
     foo.name = "I am a banana";
-    foo.files = [
-      // These are supposed to be handles, but we fake them with integers.
-      23423782, 32549823, 98320423, 38502383, 92834093,
-    ];
+    // This is supposed to be a handle, but we fake it with an integer.
+    foo.source = 23423782;
 
     var messageName = 31;
-    var payloadSize = 232;
+    var payloadSize = 192;
 
     var builder = new codec.MessageBuilder(messageName, payloadSize);
     builder.encodeStruct(sample.Foo, foo);
@@ -90,20 +88,19 @@ define([
     var message = builder.finish();
 
     var expectedMemory = new Uint8Array([
-      /*  0: */  240,    0,    0,    0,   31,    0,    0,    0,
-      /*  8: */   64,    0,    0,    0,   10,    0,    0,    0,
+      /*  0: */  200,    0,    0,    0,   31,    0,    0,    0,
+      /*  8: */   56,    0,    0,    0,   10,    0,    0,    0,
       /* 16: */ 0xD5, 0xB4, 0x12, 0x02, 0x93, 0x6E, 0x01,    0,
       /* 24: */    5,    0,    0,    0,    0,    0,    0,    0,
-      /* 32: */   40,    0,    0,    0,    0,    0,    0,    0,
+      /* 32: */   32,    0,    0,    0,    0,    0,    0,    0,
     ]);
     // TODO(abarth): Test more of the message's raw memory.
     var actualMemory = new Uint8Array(message.memory.buffer,
                                       0, expectedMemory.length);
-
     expect(actualMemory).toEqual(expectedMemory);
 
     var expectedHandles = [
-      23423782, 32549823, 98320423, 38502383, 92834093,
+      23423782,
     ];
 
     expect(message.handles).toEqual(expectedHandles);
@@ -127,7 +124,7 @@ define([
 
     expect(foo2.extra_bars).toEqual(foo.extra_bars);
     expect(foo2.name).toBe(foo.name);
-    expect(foo2.files).toEqual(foo.files);
+    expect(foo2.source).toEqual(foo.source);
   }
 
   function testAlign() {
diff --git a/mojo/apps/js/bindings/connector_unittests.js b/mojo/apps/js/bindings/connector_unittests.js
index 8aa533f..650cf78 100644
--- a/mojo/apps/js/bindings/connector_unittests.js
+++ b/mojo/apps/js/bindings/connector_unittests.js
@@ -90,6 +90,7 @@ define([
 
   var pipe = core.createMessagePipe();
   var anotherPipe = core.createMessagePipe();
+  var sourcePipe = core.createMessagePipe();
 
   var connection0 = new connector.Connection(
       pipe.handle0, ServiceImpl, sample.ServiceClientProxy);
@@ -100,6 +101,7 @@ define([
   var foo = new sample.Foo();
   foo.bar = new sample.Bar();
   foo.name = "Example name";
+  foo.source = sourcePipe.handle0;
   connection1.remote.frobinate(foo, true, anotherPipe.handle0);
 
   mockSupport.pumpOnce(core.RESULT_OK);
@@ -112,6 +114,11 @@ define([
 
   expect(mockSupport.numberOfWaitingCallbacks()).toBe(0);
 
+  // sourcePipe.handle0 was closed automatically when sent over IPC.
+  expect(core.close(sourcePipe.handle0)).toBe(core.RESULT_INVALID_ARGUMENT);
+  // sourcePipe.handle1 hasn't been closed yet.
+  expect(core.close(sourcePipe.handle1)).toBe(core.RESULT_OK);
+
   // anotherPipe.handle0 was closed automatically when sent over IPC.
   expect(core.close(anotherPipe.handle0)).toBe(core.RESULT_INVALID_ARGUMENT);
   // anotherPipe.handle1 hasn't been closed yet.
diff --git a/mojo/examples/sample_app/native_viewport_client_impl.cc b/mojo/examples/sample_app/native_viewport_client_impl.cc
index 5d70df1..c956051 100644
--- a/mojo/examples/sample_app/native_viewport_client_impl.cc
+++ b/mojo/examples/sample_app/native_viewport_client_impl.cc
@@ -26,7 +26,7 @@ void NativeViewportClientImpl::Open() {
   CreateMessagePipe(&gles2, &gles2_client);
 
   gles2_client_.reset(new GLES2ClientImpl(gles2.Pass()));
-  service_->CreateGLES2Context(gles2_client.release());
+  service_->CreateGLES2Context(gles2_client.Pass());
 }
 
 void NativeViewportClientImpl::DidOpen() {
diff --git a/mojo/mojo_public.gypi b/mojo/mojo_public.gypi
index 01dd9a2..ea671cb 100644
--- a/mojo/mojo_public.gypi
+++ b/mojo/mojo_public.gypi
@@ -27,10 +27,12 @@
       ],
       'sources': [
         'public/tests/bindings_connector_unittest.cc',
+        'public/tests/bindings_handle_passing_unittest.cc',
         'public/tests/bindings_remote_ptr_unittest.cc',
         'public/tests/bindings_type_conversion_unittest.cc',
         'public/tests/buffer_unittest.cc',
         'public/tests/math_calculator.mojom',
+        'public/tests/sample_factory.mojom',
         'public/tests/system_core_cpp_unittest.cc',
         'public/tests/system_core_unittest.cc',
         'public/tests/test_structs.mojom',
diff --git a/mojo/public/bindings/generators/cpp_templates/interface_stub_case b/mojo/public/bindings/generators/cpp_templates/interface_stub_case
index f02702a..808cdb3 100644
--- a/mojo/public/bindings/generators/cpp_templates/interface_stub_case
+++ b/mojo/public/bindings/generators/cpp_templates/interface_stub_case
@@ -3,8 +3,9 @@
           reinterpret_cast<internal::${CLASS}_${METHOD}_Params_Data*>(
               message->data->payload);
 
-      if (!mojo::internal::DecodePointersAndHandles(params, *message))
+      if (!mojo::internal::DecodePointersAndHandles(params, message))
         return false;
       $METHOD_CALL
+      mojo::internal::CloseHandles(params);
       break;
     }
diff --git a/mojo/public/bindings/generators/cpp_templates/module.cc-template b/mojo/public/bindings/generators/cpp_templates/module.cc-template
index 404d923..e8100fb 100644
--- a/mojo/public/bindings/generators/cpp_templates/module.cc-template
+++ b/mojo/public/bindings/generators/cpp_templates/module.cc-template
@@ -26,6 +26,8 @@ $PARAM_DEFINITIONS
 
 $STRUCT_DEFINITIONS
 
+$STRUCT_DESTRUCTORS
+
 }  // namespace internal
 
 $STRUCT_BUILDER_DEFINITIONS
diff --git a/mojo/public/bindings/generators/cpp_templates/params_serialization b/mojo/public/bindings/generators/cpp_templates/params_serialization
index c3a57b5..0a89cd9 100644
--- a/mojo/public/bindings/generators/cpp_templates/params_serialization
+++ b/mojo/public/bindings/generators/cpp_templates/params_serialization
@@ -1,6 +1,10 @@
 template <>
 class ObjectTraits<$CLASS> {
  public:
+  static void CloseHandles($CLASS* $NAME) {
+$CLOSES
+  }
+
   static void EncodePointersAndHandles(
       $CLASS* $NAME,
       std::vector<Handle>* handles) {
@@ -10,7 +14,7 @@ $ENCODE_HANDLES
 
   static bool DecodePointersAndHandles(
       $CLASS* $NAME,
-      const Message& message) {
+      Message* message) {
 $DECODES
 $DECODE_HANDLES
     return true;
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_builder_definition b/mojo/public/bindings/generators/cpp_templates/struct_builder_definition
index 0e31319..0bc36d7 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_builder_definition
+++ b/mojo/public/bindings/generators/cpp_templates/struct_builder_definition
@@ -1,5 +1,5 @@
 $CLASS::Builder::Builder(mojo::Buffer* buf)
-    : data_(Data::New(buf)) {
+    : data_(Data::New(buf, $DTOR)) {
 }
 
 $CLASS $CLASS::Builder::Finish() {
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_declaration b/mojo/public/bindings/generators/cpp_templates/struct_declaration
index 138028b..a780d65 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_declaration
+++ b/mojo/public/bindings/generators/cpp_templates/struct_declaration
@@ -2,7 +2,7 @@ class $CLASS {
  public:
   typedef $WRAPPER Wrapper;
 
-  static $CLASS* New(mojo::Buffer* buf);
+  static $CLASS* New(mojo::Buffer* buf, mojo::Buffer::Destructor dtor = NULL);
 
 $SETTERS
 
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_definition b/mojo/public/bindings/generators/cpp_templates/struct_definition
index cbfebc5..e69d787 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_definition
+++ b/mojo/public/bindings/generators/cpp_templates/struct_definition
@@ -1,6 +1,6 @@
 // static
-$CLASS* $CLASS::New(mojo::Buffer* buf) {
-  return new (buf->Allocate(sizeof($CLASS))) $CLASS();
+$CLASS* $CLASS::New(mojo::Buffer* buf, mojo::Buffer::Destructor dtor) {
+  return new (buf->Allocate(sizeof($CLASS), dtor)) $CLASS();
 }
 
 $CLASS::$CLASS() {
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_destructor b/mojo/public/bindings/generators/cpp_templates/struct_destructor
new file mode 100644
index 0000000..6b5e67e
--- /dev/null
+++ b/mojo/public/bindings/generators/cpp_templates/struct_destructor
@@ -0,0 +1,4 @@
+static void ${CLASS}_Data_Destructor(void* address) {
+  ${CLASS}_Data* data = static_cast<${CLASS}_Data*>(address);
+  $BODY
+}
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_serialization b/mojo/public/bindings/generators/cpp_templates/struct_serialization
index 5b9d45d2..c321c82 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_serialization
+++ b/mojo/public/bindings/generators/cpp_templates/struct_serialization
@@ -7,8 +7,8 @@ $ENCODE_HANDLES
 
 // static
 bool ObjectTraits<$CLASS>::DecodePointersAndHandles(
-    $CLASS* $NAME, const mojo::Message& message) {
+    $CLASS* $NAME, mojo::Message* message) {
 $DECODES
 $DECODE_HANDLES
   return true;
-}
\ No newline at end of file
+}
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_serialization_definition b/mojo/public/bindings/generators/cpp_templates/struct_serialization_definition
index 1d688bb..b404276 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_serialization_definition
+++ b/mojo/public/bindings/generators/cpp_templates/struct_serialization_definition
@@ -10,7 +10,15 @@ $CLASS* ObjectTraits<$CLASS>::Clone(
   $CLASS* clone = $CLASS::New(buf);
   memcpy(clone, $NAME, sizeof(*$NAME));
 $CLONES
+$HANDLE_RELEASES
   return clone;
 }
 
+// static
+void ObjectTraits<$CLASS>::CloseHandles(
+    $CLASS* $NAME) {
+$CLOSES
+$DTOR
+}
+
 $SERIALIZATION
diff --git a/mojo/public/bindings/generators/cpp_templates/struct_serialization_traits b/mojo/public/bindings/generators/cpp_templates/struct_serialization_traits
index cbb739b..9975742 100644
--- a/mojo/public/bindings/generators/cpp_templates/struct_serialization_traits
+++ b/mojo/public/bindings/generators/cpp_templates/struct_serialization_traits
@@ -3,8 +3,9 @@ class ObjectTraits<$FULL_CLASS> {
  public:
   static size_t ComputeSizeOf(const $FULL_CLASS* $NAME);
   static $FULL_CLASS* Clone(const $FULL_CLASS* $NAME, Buffer* buf);
+  static void CloseHandles($FULL_CLASS* $NAME);
   static void EncodePointersAndHandles($FULL_CLASS* $NAME,
                                        std::vector<mojo::Handle>* handles);
   static bool DecodePointersAndHandles($FULL_CLASS* $NAME,
-                                       const mojo::Message& message);
+                                       mojo::Message* message);
 };
diff --git a/mojo/public/bindings/generators/cpp_templates/template_declaration b/mojo/public/bindings/generators/cpp_templates/template_declaration
index 9b923e4..fe9c82c 100644
--- a/mojo/public/bindings/generators/cpp_templates/template_declaration
+++ b/mojo/public/bindings/generators/cpp_templates/template_declaration
@@ -1,10 +1,12 @@
 template <>
 class ObjectTraits<$NAMESPACE::internal::$CLASS> {
  public:
+  static void CloseHandles(
+      $NAMESPACE::internal::$CLASS* params);
   static void EncodePointersAndHandles(
       $NAMESPACE::internal::$CLASS* params,
       std::vector<mojo::Handle>* handles);
   static bool DecodePointersAndHandles(
       $NAMESPACE::internal::$CLASS* params,
-      const mojo::Message& message);
+      mojo::Message* message);
 };
diff --git a/mojo/public/bindings/generators/mojom.py b/mojo/public/bindings/generators/mojom.py
index 658e2b5..84804dc 100644
--- a/mojo/public/bindings/generators/mojom.py
+++ b/mojo/public/bindings/generators/mojom.py
@@ -17,19 +17,20 @@ class Kind(object):
 
 
 # Initialize the set of primitive types. These can be accessed by clients.
-BOOL   = Kind('b')
-INT8   = Kind('i8')
-INT16  = Kind('i16')
-INT32  = Kind('i32')
-INT64  = Kind('i64')
-UINT8  = Kind('u8')
-UINT16 = Kind('u16')
-UINT32 = Kind('u32')
-UINT64 = Kind('u64')
-FLOAT  = Kind('f')
-DOUBLE = Kind('d')
-STRING = Kind('s')
-HANDLE = Kind('h')
+BOOL    = Kind('b')
+INT8    = Kind('i8')
+INT16   = Kind('i16')
+INT32   = Kind('i32')
+INT64   = Kind('i64')
+UINT8   = Kind('u8')
+UINT16  = Kind('u16')
+UINT32  = Kind('u32')
+UINT64  = Kind('u64')
+FLOAT   = Kind('f')
+DOUBLE  = Kind('d')
+STRING  = Kind('s')
+HANDLE  = Kind('h')
+MSGPIPE = Kind('h:m')
 
 
 # Collection of all Primitive types
@@ -46,7 +47,8 @@ PRIMITIVES = (
   FLOAT,
   DOUBLE,
   STRING,
-  HANDLE
+  HANDLE,
+  MSGPIPE
 )
 
 
diff --git a/mojo/public/bindings/generators/mojom_cpp_generator.py b/mojo/public/bindings/generators/mojom_cpp_generator.py
index 76e5930..354263e 100644
--- a/mojo/public/bindings/generators/mojom_cpp_generator.py
+++ b/mojo/public/bindings/generators/mojom_cpp_generator.py
@@ -46,6 +46,8 @@ class CPPGenerator(mojom_generator.Generator):
     Template(" +\n      mojo::internal::ComputeSizeOf($NAME->$FIELD())")
   struct_serialization_clone_template = Template(
       "  clone->set_$FIELD(mojo::internal::Clone($NAME->$FIELD(), buf));")
+  struct_serialization_handle_release_template = Template(
+      "  (void) $NAME->$FIELD();")
   struct_serialization_encode_template = Template(
       "  Encode(&$NAME->${FIELD}_, handles);")
   struct_serialization_encode_handle_template = Template(
@@ -54,9 +56,16 @@ class CPPGenerator(mojom_generator.Generator):
       "  if (!Decode(&$NAME->${FIELD}_, message))\n"
       "    return false;")
   struct_serialization_decode_handle_template = Template(
-      "  if (!DecodeHandle(&$NAME->${FIELD}_, message.handles))\n"
+      "  if (!DecodeHandle(&$NAME->${FIELD}_, &message->handles))\n"
       "    return false;")
-  param_set_template = Template("  params->set_$NAME($NAME);")
+  struct_destructor_body_template = Template(
+      "mojo::MakeScopedHandle(data->$FIELD());")
+  close_handles_template = Template(
+      "  mojo::internal::CloseHandles($NAME->${FIELD}_.ptr);")
+  param_set_template = Template(
+      "  params->set_$NAME($NAME);")
+  param_handle_set_template = Template(
+      "  params->set_$NAME($NAME.release());")
   param_struct_set_template = Template(
       "  params->set_$NAME(\n"
       "      mojo::internal::Clone(mojo::internal::Unwrap($NAME),\n"
@@ -66,6 +75,7 @@ class CPPGenerator(mojom_generator.Generator):
       "      mojo::internal::Unwrap($NAME));")
   field_template = Template("  $TYPE ${FIELD}_;")
   bool_field_template = Template("  uint8_t ${FIELD}_ : 1;")
+  handle_field_template = Template("  mutable $TYPE ${FIELD}_;")
   setter_template = \
       Template("  void set_$FIELD($TYPE $FIELD) { ${FIELD}_ = $FIELD; }")
   ptr_setter_template = \
@@ -74,34 +84,44 @@ class CPPGenerator(mojom_generator.Generator):
       Template("  $TYPE $FIELD() const { return ${FIELD}_; }")
   ptr_getter_template = \
       Template("  const $TYPE $FIELD() const { return ${FIELD}_.ptr; }")
+  handle_getter_template = \
+      Template("  $TYPE $FIELD() const { " \
+               "return mojo::internal::FetchAndReset(&${FIELD}_); }")
   wrapper_setter_template = \
       Template("    void set_$FIELD($TYPE $FIELD) { " \
                "data_->set_$FIELD($FIELD); }")
   wrapper_obj_setter_template = \
       Template("    void set_$FIELD($TYPE $FIELD) { " \
                "data_->set_$FIELD(mojo::internal::Unwrap($FIELD)); }")
+  wrapper_handle_setter_template = \
+      Template("    void set_$FIELD($TYPE $FIELD) { " \
+               "data_->set_$FIELD($FIELD.release()); }")
   wrapper_getter_template = \
       Template("  $TYPE $FIELD() const { return data_->$FIELD(); }")
   wrapper_obj_getter_template = \
       Template("  const $TYPE $FIELD() const { " \
                "return mojo::internal::Wrap(data_->$FIELD()); }")
+  wrapper_handle_getter_template = \
+      Template("  $TYPE $FIELD() const { " \
+               "return mojo::MakeScopedHandle(data_->$FIELD()); }")
   pad_template = Template("  uint8_t _pad${COUNT}_[$PAD];")
   templates  = {}
   HEADER_SIZE = 8
 
   kind_to_type = {
-    mojom.BOOL:   "bool",
-    mojom.INT8:   "int8_t",
-    mojom.UINT8:  "uint8_t",
-    mojom.INT16:  "int16_t",
-    mojom.UINT16: "uint16_t",
-    mojom.INT32:  "int32_t",
-    mojom.UINT32: "uint32_t",
-    mojom.FLOAT:  "float",
-    mojom.HANDLE: "mojo::Handle",
-    mojom.INT64:  "int64_t",
-    mojom.UINT64: "uint64_t",
-    mojom.DOUBLE: "double",
+    mojom.BOOL:    "bool",
+    mojom.INT8:    "int8_t",
+    mojom.UINT8:   "uint8_t",
+    mojom.INT16:   "int16_t",
+    mojom.UINT16:  "uint16_t",
+    mojom.INT32:   "int32_t",
+    mojom.UINT32:  "uint32_t",
+    mojom.FLOAT:   "float",
+    mojom.HANDLE:  "mojo::Handle",
+    mojom.MSGPIPE: "mojo::MessagePipeHandle",
+    mojom.INT64:   "int64_t",
+    mojom.UINT64:  "uint64_t",
+    mojom.DOUBLE:  "double",
   }
 
   @classmethod
@@ -142,6 +162,8 @@ class CPPGenerator(mojom_generator.Generator):
     subs = {'FIELD': field.name, 'TYPE': cls.GetType(field.kind)}
     if mojom_generator.IsObjectKind(field.kind):
       return cls.ptr_getter_template.substitute(subs)
+    elif mojom_generator.IsHandleKind(field.kind):
+      return cls.handle_getter_template.substitute(subs)
     else:
       return cls.getter_template.substitute(subs)
 
@@ -161,6 +183,10 @@ class CPPGenerator(mojom_generator.Generator):
       return "mojo::Array<%s >" % cls.GetWrapperType(kind.kind)
     if kind.spec == 's':
       return "mojo::String"
+    if kind.spec == 'h':
+      return "mojo::ScopedHandle"
+    if kind.spec == 'h:m':
+      return "mojo::ScopedMessagePipeHandle"
     return cls.kind_to_type[kind]
 
   @classmethod
@@ -171,6 +197,10 @@ class CPPGenerator(mojom_generator.Generator):
       return "const mojo::Array<%s >&" % cls.GetWrapperType(kind.kind)
     if kind.spec == 's':
       return "const mojo::String&"
+    if kind.spec == 'h':
+      return "mojo::ScopedHandle"
+    if kind.spec == 'h:m':
+      return "mojo::ScopedMessagePipeHandle"
     return cls.kind_to_type[kind]
 
   @classmethod
@@ -178,6 +208,8 @@ class CPPGenerator(mojom_generator.Generator):
     subs = {'FIELD': field.name, 'TYPE': cls.GetWrapperType(field.kind)}
     if mojom_generator.IsObjectKind(field.kind):
       return cls.wrapper_obj_getter_template.substitute(subs)
+    elif mojom_generator.IsHandleKind(field.kind):
+      return cls.wrapper_handle_getter_template.substitute(subs)
     else:
       return cls.wrapper_getter_template.substitute(subs)
 
@@ -186,6 +218,8 @@ class CPPGenerator(mojom_generator.Generator):
     subs = {'FIELD': field.name, 'TYPE': cls.GetConstWrapperType(field.kind)}
     if mojom_generator.IsObjectKind(field.kind):
       return cls.wrapper_obj_setter_template.substitute(subs)
+    elif mojom_generator.IsHandleKind(field.kind):
+      return cls.wrapper_handle_setter_template.substitute(subs)
     else:
       return cls.wrapper_setter_template.substitute(subs)
 
@@ -194,6 +228,9 @@ class CPPGenerator(mojom_generator.Generator):
     kind = field.kind
     if kind.spec == 'b':
       return cls.bool_field_template.substitute(FIELD=field.name)
+    if mojom_generator.IsHandleKind(kind):
+      return cls.handle_field_template.substitute(FIELD=field.name,
+                                                  TYPE=cls.kind_to_type[kind])
     itype = None
     if isinstance(kind, mojom.Struct):
       itype = "mojo::internal::StructPointer<%s_Data>" % kind.name
@@ -210,6 +247,8 @@ class CPPGenerator(mojom_generator.Generator):
     line = None
     if mojom_generator.IsObjectKind(kind):
       line = "mojo::internal::Wrap(params->%s())" % (name)
+    elif mojom_generator.IsHandleKind(kind):
+      line = "mojo::MakeScopedHandle(params->%s())" % (name)
     else:
       line = "params->%s()" % name
     return line
@@ -240,10 +279,25 @@ class CPPGenerator(mojom_generator.Generator):
   def GetHandleFields(cls, ps):
     fields = []
     for pf in ps.packed_fields:
-      if pf.field.kind.spec == 'h':
+      if mojom_generator.IsHandleKind(pf.field.kind):
         fields.append(pf.field)
     return fields
 
+  @classmethod
+  def IsStructWithHandles(cls, struct):
+    for field in struct.fields:
+      if mojom_generator.IsHandleKind(field.kind):
+        return True
+    return False
+
+  @classmethod
+  def GetStructsWithHandles(cls, structs):
+    result = []
+    for struct in structs:
+      if cls.IsStructWithHandles(struct):
+        result.append(struct)
+    return result
+
   def GetHeaderGuard(self, name):
     return "MOJO_GENERATED_BINDINGS_%s_%s_H_" % \
         (self.module.name.upper(), name.upper())
@@ -307,6 +361,7 @@ class CPPGenerator(mojom_generator.Generator):
   def GetStructSerialization(
       self, class_name, param_name, ps, template, indent = None):
     struct = ps.struct
+    closes = Lines(self.close_handles_template, indent)
     encodes = Lines(self.struct_serialization_encode_template, indent)
     encode_handles = \
         Lines(self.struct_serialization_encode_handle_template, indent)
@@ -319,6 +374,7 @@ class CPPGenerator(mojom_generator.Generator):
       substitutions = {'NAME': param_name, 'FIELD': field.name}
       encodes.Add(substitutions)
       decodes.Add(substitutions)
+      closes.Add(substitutions)
     for field in handle_fields:
       substitutions = {'NAME': param_name, 'FIELD': field.name}
       encode_handles.Add(substitutions)
@@ -327,6 +383,7 @@ class CPPGenerator(mojom_generator.Generator):
         CLASS = \
             "%s::internal::%s" % (self.module.namespace, class_name + '_Data'),
         NAME = param_name,
+        CLOSES = closes,
         ENCODES = encodes,
         DECODES = decodes,
         ENCODE_HANDLES = encode_handles,
@@ -435,10 +492,34 @@ class CPPGenerator(mojom_generator.Generator):
             NUM_FIELDS = len(s.fields)),
             self.module.structs));
 
+  def GetStructDestructorBody(self, struct):
+    body = Lines(self.struct_destructor_body_template)
+    for field in struct.fields:
+      if mojom_generator.IsHandleKind(field.kind):
+        body.Add(FIELD=field.name)
+    return body
+
+  def GetStructDestructors(self):
+    template = self.GetTemplate("struct_destructor")
+    return '\n'.join(map(
+        lambda s: template.substitute(
+            CLASS = s.name,
+            BODY = self.GetStructDestructorBody(s)),
+            self.GetStructsWithHandles(self.module.structs)));
+
+  def GetStructDestructorAddress(self, struct):
+    if self.IsStructWithHandles(struct):
+      return '&internal::' + struct.name + '_Data_Destructor';
+    return 'NULL'
+
   def GetStructBuilderDefinitions(self):
     template = self.GetTemplate("struct_builder_definition")
+    dtor = 'NULL'
     return '\n'.join(map(
-        lambda s: template.substitute(CLASS = s.name), self.module.structs));
+        lambda s: template.substitute(
+            CLASS = s.name,
+            DTOR = self.GetStructDestructorAddress(s)),
+            self.module.structs));
 
   def GetInterfaceDefinition(self, interface):
     cases = []
@@ -453,6 +534,9 @@ class CPPGenerator(mojom_generator.Generator):
           sets.append(
               self.param_struct_set_template.substitute(NAME=param.name))
           computes.Add(NAME=param.name)
+        elif mojom_generator.IsHandleKind(param.kind):
+          sets.append(
+              self.param_handle_set_template.substitute(NAME=param.name))
         else:
           sets.append(self.param_set_template.substitute(NAME=param.name))
       params_list = map(
@@ -487,7 +571,10 @@ class CPPGenerator(mojom_generator.Generator):
     ps = mojom_pack.PackedStruct(struct)
     param_name = mojom_generator.CamelToUnderscores(struct.name)
 
+    dtor = ''
+    closes = Lines(self.close_handles_template)
     clones = Lines(self.struct_serialization_clone_template)
+    handle_releases = Lines(self.struct_serialization_handle_release_template)
     sizes = "  return sizeof(*%s)" % param_name
     fields = self.GetSerializedFields(ps)
     for field in fields:
@@ -495,6 +582,13 @@ class CPPGenerator(mojom_generator.Generator):
       sizes += \
           self.struct_serialization_compute_template.substitute(substitutions)
       clones.Add(substitutions)
+      closes.Add(substitutions)
+    handle_fields = self.GetHandleFields(ps)
+    for field in handle_fields:
+      substitutions = {'NAME': param_name, 'FIELD': field.name}
+      handle_releases.Add(substitutions)
+    if len(handle_fields) > 0:
+      dtor = "  %s_Data_Destructor(%s);" % (struct.name, param_name)
     sizes += ";"
     serialization = self.GetStructSerialization(
       struct.name, param_name, ps, self.GetTemplate("struct_serialization"))
@@ -503,6 +597,9 @@ class CPPGenerator(mojom_generator.Generator):
         CLASS = "%s::internal::%s_Data" % (self.module.namespace, struct.name),
         SIZES = sizes,
         CLONES = clones,
+        HANDLE_RELEASES = handle_releases,
+        CLOSES = closes,
+        DTOR = dtor,
         SERIALIZATION = serialization)
 
   def GetStructSerializationDefinitions(self):
@@ -537,6 +634,7 @@ class CPPGenerator(mojom_generator.Generator):
         HEADER = self.GetHeaderFile(self.module.name),
         PARAM_DEFINITIONS = self.GetParamsDefinitions(),
         STRUCT_DEFINITIONS = self.GetStructDefinitions(),
+        STRUCT_DESTRUCTORS = self.GetStructDestructors(),
         STRUCT_BUILDER_DEFINITIONS = self.GetStructBuilderDefinitions(),
         INTERFACE_DEFINITIONS = self.GetInterfaceDefinitions(),
         STRUCT_SERIALIZATION_DEFINITIONS =
diff --git a/mojo/public/bindings/generators/mojom_generator.py b/mojo/public/bindings/generators/mojom_generator.py
index 4320bbb..f2ee3e0 100644
--- a/mojo/public/bindings/generators/mojom_generator.py
+++ b/mojo/public/bindings/generators/mojom_generator.py
@@ -18,6 +18,9 @@ def GetStructFromMethod(interface, method):
 def IsObjectKind(kind):
   return isinstance(kind, (mojom.Struct, mojom.Array)) or kind.spec == 's'
 
+def IsHandleKind(kind):
+  return kind.spec.startswith('h')
+
 def CamelToUnderscores(camel):
   s = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', camel)
   return re.sub('([a-z0-9])([A-Z])', r'\1_\2', s).lower()
diff --git a/mojo/public/bindings/generators/mojom_js_generator.py b/mojo/public/bindings/generators/mojom_js_generator.py
index 2bfe9e8..82b9b8e 100644
--- a/mojo/public/bindings/generators/mojom_js_generator.py
+++ b/mojo/public/bindings/generators/mojom_js_generator.py
@@ -13,19 +13,20 @@ from functools import partial
 from template_expander import UseJinja
 
 _kind_to_default_value = {
-  mojom.BOOL:   "false",
-  mojom.INT8:   "0",
-  mojom.UINT8:  "0",
-  mojom.INT16:  "0",
-  mojom.UINT16: "0",
-  mojom.INT32:  "0",
-  mojom.UINT32: "0",
-  mojom.FLOAT:  "0",
-  mojom.HANDLE: "core.kInvalidHandle",
-  mojom.INT64:  "0",
-  mojom.UINT64: "0",
-  mojom.DOUBLE: "0",
-  mojom.STRING: '""',
+  mojom.BOOL:    "false",
+  mojom.INT8:    "0",
+  mojom.UINT8:   "0",
+  mojom.INT16:   "0",
+  mojom.UINT16:  "0",
+  mojom.INT32:   "0",
+  mojom.UINT32:  "0",
+  mojom.FLOAT:   "0",
+  mojom.HANDLE:  "core.kInvalidHandle",
+  mojom.MSGPIPE: "core.kInvalidHandle",
+  mojom.INT64:   "0",
+  mojom.UINT64:  "0",
+  mojom.DOUBLE:  "0",
+  mojom.STRING:  '""',
 }
 
 
@@ -51,19 +52,20 @@ def PayloadSize(packed):
 
 
 _kind_to_javascript_type = {
-  mojom.BOOL:   "codec.Uint8",
-  mojom.INT8:   "codec.Int8",
-  mojom.UINT8:  "codec.Uint8",
-  mojom.INT16:  "codec.Int16",
-  mojom.UINT16: "codec.Uint16",
-  mojom.INT32:  "codec.Int32",
-  mojom.UINT32: "codec.Uint32",
-  mojom.FLOAT:  "codec.Float",
-  mojom.HANDLE: "codec.Handle",
-  mojom.INT64:  "codec.Int64",
-  mojom.UINT64: "codec.Uint64",
-  mojom.DOUBLE: "codec.Double",
-  mojom.STRING: "codec.String",
+  mojom.BOOL:    "codec.Uint8",
+  mojom.INT8:    "codec.Int8",
+  mojom.UINT8:   "codec.Uint8",
+  mojom.INT16:   "codec.Int16",
+  mojom.UINT16:  "codec.Uint16",
+  mojom.INT32:   "codec.Int32",
+  mojom.UINT32:  "codec.Uint32",
+  mojom.FLOAT:   "codec.Float",
+  mojom.HANDLE:  "codec.Handle",
+  mojom.MSGPIPE: "codec.Handle",
+  mojom.INT64:   "codec.Int64",
+  mojom.UINT64:  "codec.Uint64",
+  mojom.DOUBLE:  "codec.Double",
+  mojom.STRING:  "codec.String",
 }
 
 
@@ -78,19 +80,20 @@ def GetJavaScriptType(kind):
 
 
 _kind_to_decode_snippet = {
-  mojom.BOOL:   "read8() & 1",
-  mojom.INT8:   "read8()",
-  mojom.UINT8:  "read8()",
-  mojom.INT16:  "read16()",
-  mojom.UINT16: "read16()",
-  mojom.INT32:  "read32()",
-  mojom.UINT32: "read32()",
-  mojom.FLOAT:  "decodeFloat()",
-  mojom.HANDLE: "decodeHandle()",
-  mojom.INT64:  "read64()",
-  mojom.UINT64: "read64()",
-  mojom.DOUBLE: "decodeDouble()",
-  mojom.STRING: "decodeStringPointer()",
+  mojom.BOOL:    "read8() & 1",
+  mojom.INT8:    "read8()",
+  mojom.UINT8:   "read8()",
+  mojom.INT16:   "read16()",
+  mojom.UINT16:  "read16()",
+  mojom.INT32:   "read32()",
+  mojom.UINT32:  "read32()",
+  mojom.FLOAT:   "decodeFloat()",
+  mojom.HANDLE:  "decodeHandle()",
+  mojom.MSGPIPE: "decodeHandle()",
+  mojom.INT64:   "read64()",
+  mojom.UINT64:  "read64()",
+  mojom.DOUBLE:  "decodeDouble()",
+  mojom.STRING:  "decodeStringPointer()",
 }
 
 
@@ -104,19 +107,20 @@ def DecodeSnippet(kind):
 
 
 _kind_to_encode_snippet = {
-  mojom.BOOL:   "write8(1 & ",
-  mojom.INT8:   "write8(",
-  mojom.UINT8:  "write8(",
-  mojom.INT16:  "write16(",
-  mojom.UINT16: "write16(",
-  mojom.INT32:  "write32(",
-  mojom.UINT32: "write32(",
-  mojom.FLOAT:  "encodeFloat(",
-  mojom.HANDLE: "encodeHandle(",
-  mojom.INT64:  "write64(",
-  mojom.UINT64: "write64(",
-  mojom.DOUBLE: "encodeDouble(",
-  mojom.STRING: "encodeStringPointer(",
+  mojom.BOOL:    "write8(1 & ",
+  mojom.INT8:    "write8(",
+  mojom.UINT8:   "write8(",
+  mojom.INT16:   "write16(",
+  mojom.UINT16:  "write16(",
+  mojom.INT32:   "write32(",
+  mojom.UINT32:  "write32(",
+  mojom.FLOAT:   "encodeFloat(",
+  mojom.HANDLE:  "encodeHandle(",
+  mojom.MSGPIPE: "encodeHandle(",
+  mojom.INT64:   "write64(",
+  mojom.UINT64:  "write64(",
+  mojom.DOUBLE:  "encodeDouble(",
+  mojom.STRING:  "encodeStringPointer(",
 }
 
 
diff --git a/mojo/public/bindings/generators/mojom_pack.py b/mojo/public/bindings/generators/mojom_pack.py
index 7aea9c4..63b70a7 100644
--- a/mojo/public/bindings/generators/mojom_pack.py
+++ b/mojo/public/bindings/generators/mojom_pack.py
@@ -13,19 +13,20 @@ import mojom
 
 class PackedField(object):
   kind_to_size = {
-    mojom.BOOL:   1,
-    mojom.INT8:   1,
-    mojom.UINT8:  1,
-    mojom.INT16:  2,
-    mojom.UINT16: 2,
-    mojom.INT32:  4,
-    mojom.UINT32: 4,
-    mojom.FLOAT:  4,
-    mojom.HANDLE: 4,
-    mojom.INT64:  8,
-    mojom.UINT64: 8,
-    mojom.DOUBLE: 8,
-    mojom.STRING: 8
+    mojom.BOOL:    1,
+    mojom.INT8:    1,
+    mojom.UINT8:   1,
+    mojom.INT16:   2,
+    mojom.UINT16:  2,
+    mojom.INT32:   4,
+    mojom.UINT32:  4,
+    mojom.FLOAT:   4,
+    mojom.HANDLE:  4,
+    mojom.MSGPIPE: 4,
+    mojom.INT64:   8,
+    mojom.UINT64:  8,
+    mojom.DOUBLE:  8,
+    mojom.STRING:  8
   }
 
   @classmethod
diff --git a/mojo/public/bindings/lib/bindings_internal.h b/mojo/public/bindings/lib/bindings_internal.h
index 2471240..1d5a24a 100644
--- a/mojo/public/bindings/lib/bindings_internal.h
+++ b/mojo/public/bindings/lib/bindings_internal.h
@@ -53,6 +53,13 @@ MOJO_COMPILE_ASSERT(sizeof(StringPointer) == 8, bad_sizeof_StringPointer);
 #pragma pack(pop)
 
 template <typename T>
+T FetchAndReset(T* value) {
+  T temp = *value;
+  *value = T();
+  return temp;
+}
+
+template <typename T>
 class WrapperHelper {
  public:
   static const T Wrap(const typename T::Data* data) {
@@ -115,6 +122,9 @@ template <> struct TypeTraits<double> {
 template <> struct TypeTraits<Handle> {
   static const bool kIsObject = false;
 };
+template <> struct TypeTraits<MessagePipeHandle> {
+  static const bool kIsObject = false;
+};
 
 template <typename T>
 struct ArrayDataTraits {
diff --git a/mojo/public/bindings/lib/bindings_serialization.cc b/mojo/public/bindings/lib/bindings_serialization.cc
index 952eac1..7b45b37 100644
--- a/mojo/public/bindings/lib/bindings_serialization.cc
+++ b/mojo/public/bindings/lib/bindings_serialization.cc
@@ -49,10 +49,11 @@ void EncodeHandle(Handle* handle, std::vector<Handle>* handles) {
   handle->set_value(static_cast<MojoHandle>(handles->size() - 1));
 }
 
-bool DecodeHandle(Handle* handle, const std::vector<Handle>& handles) {
-  if (handle->value() >= handles.size())
+bool DecodeHandle(Handle* handle, std::vector<Handle>* handles) {
+  if (handle->value() >= handles->size())
     return false;
-  *handle = handles[handle->value()];
+  // Just leave holes in the vector so we don't screw up other indices.
+  *handle = FetchAndReset(&handles->at(handle->value()));
   return true;
 }
 
@@ -69,9 +70,9 @@ void ArrayHelper<Handle>::EncodePointersAndHandles(
 bool ArrayHelper<Handle>::DecodePointersAndHandles(
     const ArrayHeader* header,
     ElementType* elements,
-    const Message& message) {
+    Message* message) {
   for (uint32_t i = 0; i < header->num_elements; ++i) {
-    if (!DecodeHandle(&elements[i], message.handles))
+    if (!DecodeHandle(&elements[i], &message->handles))
       return false;
   }
   return true;
diff --git a/mojo/public/bindings/lib/bindings_serialization.h b/mojo/public/bindings/lib/bindings_serialization.h
index ac08984..863aed4 100644
--- a/mojo/public/bindings/lib/bindings_serialization.h
+++ b/mojo/public/bindings/lib/bindings_serialization.h
@@ -39,7 +39,7 @@ bool ValidatePointer(const void* ptr, const Message& message);
 // Handles are encoded as indices into a vector of handles. These functions
 // manipulate the value of |handle|, mapping it to and from an index.
 void EncodeHandle(Handle* handle, std::vector<Handle>* handles);
-bool DecodeHandle(Handle* handle, const std::vector<Handle>& handles);
+bool DecodeHandle(Handle* handle, std::vector<Handle>* handles);
 
 // All objects (structs and arrays) support the following operations:
 //  - computing size
@@ -61,13 +61,19 @@ inline T* Clone(const T* obj, Buffer* buf) {
 }
 
 template <typename T>
+inline void CloseHandles(T* obj) {
+  if (obj)
+    ObjectTraits<T>::CloseHandles(obj);
+}
+
+template <typename T>
 inline void EncodePointersAndHandles(T* obj,
                                      std::vector<Handle>* handles) {
   ObjectTraits<T>::EncodePointersAndHandles(obj, handles);
 }
 
 template <typename T>
-inline bool DecodePointersAndHandles(T* obj, const Message& message) {
+inline bool DecodePointersAndHandles(T* obj, Message* message) {
   return ObjectTraits<T>::DecodePointersAndHandles(obj, message);
 }
 
@@ -82,10 +88,10 @@ inline void Encode(T* obj, std::vector<Handle>* handles) {
 }
 
 template <typename T>
-inline bool Decode(T* obj, const Message& message) {
+inline bool Decode(T* obj, Message* message) {
   DecodePointer(&obj->offset, &obj->ptr);
   if (obj->ptr) {
-    if (!ValidatePointer(obj->ptr, message))
+    if (!ValidatePointer(obj->ptr, *message))
       return false;
     if (!DecodePointersAndHandles(obj->ptr, message))
       return false;
@@ -118,7 +124,7 @@ struct ArrayHelper {
   }
   static bool DecodePointersAndHandles(const ArrayHeader* header,
                                        ElementType* elements,
-                                       const Message& message) {
+                                       Message* message) {
     return true;
   }
 };
@@ -142,7 +148,7 @@ struct ArrayHelper<Handle> {
                                        std::vector<Handle>* handles);
   static bool DecodePointersAndHandles(const ArrayHeader* header,
                                        ElementType* elements,
-                                       const Message& message);
+                                       Message* message);
 };
 
 template <typename P>
@@ -172,7 +178,7 @@ struct ArrayHelper<P*> {
   }
   static bool DecodePointersAndHandles(const ArrayHeader* header,
                                        ElementType* elements,
-                                       const Message& message) {
+                                       Message* message) {
     for (uint32_t i = 0; i < header->num_elements; ++i) {
       if (!Decode(&elements[i], message))
         return false;
@@ -200,6 +206,10 @@ class ObjectTraits<Array_Data<T> > {
     return clone;
   }
 
+  static void CloseHandles(Array_Data<T>* array) {
+    // TODO(darin): Implement!
+  }
+
   static void EncodePointersAndHandles(Array_Data<T>* array,
                                        std::vector<Handle>* handles) {
     ArrayHelper<T>::EncodePointersAndHandles(&array->header_, array->storage(),
@@ -207,7 +217,7 @@ class ObjectTraits<Array_Data<T> > {
   }
 
   static bool DecodePointersAndHandles(Array_Data<T>* array,
-                                       const Message& message) {
+                                       Message* message) {
     return ArrayHelper<T>::DecodePointersAndHandles(&array->header_,
                                                     array->storage(),
                                                     message);
diff --git a/mojo/public/bindings/lib/buffer.cc b/mojo/public/bindings/lib/buffer.cc
index eb40126..3265b80 100644
--- a/mojo/public/bindings/lib/buffer.cc
+++ b/mojo/public/bindings/lib/buffer.cc
@@ -45,6 +45,11 @@ ScratchBuffer::ScratchBuffer()
 }
 
 ScratchBuffer::~ScratchBuffer() {
+  // Invoke destructors in reverse order to mirror allocation order.
+  std::deque<PendingDestructor>::reverse_iterator it;
+  for (it = pending_dtors_.rbegin(); it != pending_dtors_.rend(); ++it)
+    it->func(it->address);
+
   while (overflow_) {
     Segment* doomed = overflow_;
     overflow_ = overflow_->next;
@@ -52,21 +57,27 @@ ScratchBuffer::~ScratchBuffer() {
   }
 }
 
-void* ScratchBuffer::Allocate(size_t delta) {
+void* ScratchBuffer::Allocate(size_t delta, Destructor func) {
   delta = internal::Align(delta);
 
   void* result = AllocateInSegment(&fixed_, delta);
-  if (result)
-    return result;
-
-  if (overflow_) {
-    result = AllocateInSegment(overflow_, delta);
-    if (result)
-      return result;
+  if (!result) {
+    if (overflow_)
+      result = AllocateInSegment(overflow_, delta);
+
+    if (!result) {
+      AddOverflowSegment(delta);
+      result = AllocateInSegment(overflow_, delta);
+    }
   }
 
-  AddOverflowSegment(delta);
-  return AllocateInSegment(overflow_, delta);
+  if (func) {
+    PendingDestructor dtor;
+    dtor.func = func;
+    dtor.address = result;
+    pending_dtors_.push_back(dtor);
+  }
+  return result;
 }
 
 void* ScratchBuffer::AllocateInSegment(Segment* segment, size_t delta) {
@@ -109,7 +120,9 @@ FixedBuffer::~FixedBuffer() {
   free(ptr_);
 }
 
-void* FixedBuffer::Allocate(size_t delta) {
+void* FixedBuffer::Allocate(size_t delta, Destructor dtor) {
+  assert(!dtor);
+
   delta = internal::Align(delta);
 
   // TODO(darin): Using <assert.h> is probably not going to cut it.
diff --git a/mojo/public/bindings/lib/buffer.h b/mojo/public/bindings/lib/buffer.h
index 37e76d2..6f0ce88 100644
--- a/mojo/public/bindings/lib/buffer.h
+++ b/mojo/public/bindings/lib/buffer.h
@@ -7,17 +7,22 @@
 
 #include <stddef.h>
 
+#include <deque>
+
 #include "mojo/public/system/macros.h"
 
 namespace mojo {
 
-// Allocations are 8-byte aligned and zero-filled.
+// Buffer provides a way to allocate memory. Allocations are 8-byte aligned and
+// zero-initialized. Allocations remain valid for the lifetime of the Buffer.
 class Buffer {
  public:
+  typedef void (*Destructor)(void* address);
+
   Buffer();
   virtual ~Buffer();
 
-  virtual void* Allocate(size_t num_bytes) = 0;
+  virtual void* Allocate(size_t num_bytes, Destructor func = NULL) = 0;
 
   static Buffer* current();
 
@@ -34,7 +39,8 @@ class ScratchBuffer : public Buffer {
   ScratchBuffer();
   virtual ~ScratchBuffer();
 
-  virtual void* Allocate(size_t num_bytes) MOJO_OVERRIDE;
+  virtual void* Allocate(size_t num_bytes, Destructor func = NULL)
+      MOJO_OVERRIDE;
 
  private:
   enum { kMinSegmentSize = 512 };
@@ -52,6 +58,12 @@ class ScratchBuffer : public Buffer {
   Segment fixed_;
   Segment* overflow_;
 
+  struct PendingDestructor {
+    Destructor func;
+    void* address;
+  };
+  std::deque<PendingDestructor> pending_dtors_;
+
   MOJO_DISALLOW_COPY_AND_ASSIGN(ScratchBuffer);
 };
 
@@ -87,7 +99,8 @@ class FixedBuffer : public Buffer {
   // Grows the buffer by |num_bytes| and returns a pointer to the start of the
   // addition. The resulting address is 8-byte aligned, and the content of the
   // memory is zero-filled.
-  virtual void* Allocate(size_t num_bytes) MOJO_OVERRIDE;
+  virtual void* Allocate(size_t num_bytes, Destructor func = NULL)
+      MOJO_OVERRIDE;
 
   size_t size() const { return size_; }
 
diff --git a/mojo/public/bindings/lib/message.cc b/mojo/public/bindings/lib/message.cc
index c9eb38d..ba255d6 100644
--- a/mojo/public/bindings/lib/message.cc
+++ b/mojo/public/bindings/lib/message.cc
@@ -16,9 +16,12 @@ Message::Message()
 
 Message::~Message() {
   free(data);
-  // TODO(davemoore): We don't close the handles because they're typically
-  // owned by the Connection. This could result in some Handle leaks. This will
-  // be fixed by a later cl.
+
+  for (std::vector<Handle>::iterator it = handles.begin(); it != handles.end();
+       ++it) {
+    if (it->is_valid())
+      CloseRaw(*it);
+  }
 }
 
 void Message::Swap(Message* other) {
diff --git a/mojo/public/bindings/mojom_bindings_generator.gypi b/mojo/public/bindings/mojom_bindings_generator.gypi
index 341e1a7..45efe76 100644
--- a/mojo/public/bindings/mojom_bindings_generator.gypi
+++ b/mojo/public/bindings/mojom_bindings_generator.gypi
@@ -32,6 +32,7 @@
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/proxy_implementation',
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_builder_definition',
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_declaration',
+        '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_destructor',
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_definition',
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_serialization',
         '<(DEPTH)/mojo/public/bindings/generators/cpp_templates/struct_serialization_definition',
diff --git a/mojo/public/bindings/parse/mojo_parser.py b/mojo/public/bindings/parse/mojo_parser.py
index 9bc9489..71bad65 100755
--- a/mojo/public/bindings/parse/mojo_parser.py
+++ b/mojo/public/bindings/parse/mojo_parser.py
@@ -51,6 +51,9 @@ class Lexer(object):
     'ARRAY',
     'ORDINAL',
 
+    'MSGPIPE',
+    'MSGPIPEARRAY',
+
     'MODULE',
     'STRUCT',
     'INTERFACE',
@@ -81,6 +84,14 @@ class Lexer(object):
   t_NUMBER     = r'\d+'
   t_ORDINAL    = r'@[0-9]*'
 
+  def t_MSGPIPE(self, t):
+    r'handle<message_pipe>'
+    return t
+
+  def t_MSGPIPEARRAY(self, t):
+    r'handle<message_pipe>\[\]'
+    return t
+
   def t_MODULE(self, t):
     r'module'
     return t
@@ -199,7 +210,9 @@ class Parser(object):
 
   def p_typename(self, p):
     """typename : NAME
-                | ARRAY"""
+                | ARRAY
+                | MSGPIPE
+                | MSGPIPEARRAY"""
     p[0] = p[1]
 
   def p_ordinal(self, p):
diff --git a/mojo/public/bindings/parse/mojo_translate.py b/mojo/public/bindings/parse/mojo_translate.py
index 472e1ce..8db79d8 100755
--- a/mojo/public/bindings/parse/mojo_translate.py
+++ b/mojo/public/bindings/parse/mojo_translate.py
@@ -23,7 +23,8 @@ def MapKind(kind):
                   'float': 'f',
                   'double': 'd',
                   'string': 's',
-                  'handle': 'h' }
+                  'handle': 'h',
+                  'handle<message_pipe>': 'h:m' }
   if kind.endswith('[]'):
     return 'a:' + MapKind(kind[0:len(kind)-2])
   if kind in map_to_kind:
diff --git a/mojo/public/bindings/sample/sample_service.mojom b/mojo/public/bindings/sample/sample_service.mojom
index 4251dd8..01b66ef 100644
--- a/mojo/public/bindings/sample/sample_service.mojom
+++ b/mojo/public/bindings/sample/sample_service.mojom
@@ -21,12 +21,12 @@ struct Foo {
   Bar bar @5;
   Bar[] extra_bars @7;
   uint8[] data @6;
-  handle[] files @9;
+  handle<message_pipe> source @9;
 };
 
 [Peer=ServiceClient]
 interface Service {
-  void Frobinate(Foo foo @0, bool baz @1, handle port @2) @0;
+  void Frobinate(Foo foo @0, bool baz @1, handle<message_pipe> port @2) @0;
 };
 
 [Peer=Service]
diff --git a/mojo/public/bindings/sample/sample_service_unittests.cc b/mojo/public/bindings/sample/sample_service_unittests.cc
index fc8d59a..51c7b49 100644
--- a/mojo/public/bindings/sample/sample_service_unittests.cc
+++ b/mojo/public/bindings/sample/sample_service_unittests.cc
@@ -54,9 +54,8 @@ Foo MakeFoo() {
   for (size_t i = 0; i < data.size(); ++i)
     data[i] = static_cast<uint8_t>(data.size() - i);
 
-  mojo::Array<mojo::Handle>::Builder files(4);
-  for (size_t i = 0; i < files.size(); ++i)
-    files[i] = mojo::Handle(static_cast<MojoHandle>(0xFFFF - i));
+  mojo::ScopedMessagePipeHandle pipe0, pipe1;
+  mojo::CreateMessagePipe(&pipe0, &pipe1);
 
   Foo::Builder foo;
   foo.set_name(name);
@@ -68,7 +67,7 @@ Foo MakeFoo() {
   foo.set_bar(bar.Finish());
   foo.set_extra_bars(extra_bars.Finish());
   foo.set_data(data.Finish());
-  foo.set_files(files.Finish());
+  foo.set_source(pipe1.Pass());
 
   return foo.Finish();
 }
@@ -107,14 +106,8 @@ void CheckFoo(const Foo& foo) {
   for (size_t i = 0; i < foo.data().size(); ++i) {
     EXPECT_EQ(static_cast<uint8_t>(foo.data().size() - i), foo.data()[i]) << i;
   }
-
-  EXPECT_EQ(4u, foo.files().size());
-  for (size_t i = 0; i < foo.files().size(); ++i)
-    EXPECT_EQ(static_cast<MojoHandle>(0xFFFF - i),
-              foo.files()[i].value()) << i;
 }
 
-
 static void PrintSpacer(int depth) {
   for (int i = 0; i < depth; ++i)
     printf("   ");
@@ -188,7 +181,6 @@ static void Print(int depth, const char* name, const Foo& foo) {
     Print(depth, "bar", foo.bar());
     Print(depth, "extra_bars", foo.extra_bars());
     Print(depth, "data", foo.data());
-    Print(depth, "files", foo.files());
     --depth;
   }
 }
@@ -211,14 +203,14 @@ static void DumpHex(const uint8_t* bytes, uint32_t num_bytes) {
 
 class ServiceImpl : public ServiceStub {
  public:
-  virtual void Frobinate(const Foo& foo, bool baz, mojo::Handle port)
+  virtual void Frobinate(const Foo& foo, bool baz,
+                         mojo::ScopedMessagePipeHandle port)
       MOJO_OVERRIDE {
     // Users code goes here to handle the incoming Frobinate message.
 
     // We mainly check that we're given the expected arguments.
     CheckFoo(foo);
     EXPECT_TRUE(baz);
-    EXPECT_EQ(static_cast<MojoHandle>(10), port.value());
 
     // Also dump the Foo structure and all of its members.
     // TODO(vtl): Make it optional, so that the test spews less?
@@ -226,7 +218,7 @@ class ServiceImpl : public ServiceStub {
     int depth = 1;
     Print(depth, "foo", foo);
     Print(depth, "baz", baz);
-    Print(depth, "port", port);
+    Print(depth, "port", port.get());
   }
 };
 
@@ -267,9 +259,10 @@ TEST(BindingsSampleTest, Basic) {
   Foo foo = MakeFoo();
   CheckFoo(foo);
 
-  mojo::Handle port(static_cast<MojoHandle>(10));
+  mojo::ScopedMessagePipeHandle port0, port1;
+  mojo::CreateMessagePipe(&port0, &port1);
 
-  service->Frobinate(foo, true, port);
+  service->Frobinate(foo, true, port0.Pass());
 }
 
 }  // namespace sample
diff --git a/mojo/public/bindings/sample/sample_service_unittests.js b/mojo/public/bindings/sample/sample_service_unittests.js
index 0adae31..9712f37 100644
--- a/mojo/public/bindings/sample/sample_service_unittests.js
+++ b/mojo/public/bindings/sample/sample_service_unittests.js
@@ -34,10 +34,7 @@ define([
       data[i] = data.length - i;
     }
 
-    var files = new Array(4);
-    for (var i = 0; i < files.length; ++i) {
-      files[i] = 0xFFFF - i;
-    }
+    var source = 0xFFFF;  // Invent a dummy handle.
 
     var foo = new sample.Foo();
     foo.name = "foopy";
@@ -49,7 +46,7 @@ define([
     foo.bar = bar;
     foo.extra_bars = extra_bars;
     foo.data = data;
-    foo.files = files;
+    foo.source = source;
     return foo;
   }
 
@@ -77,9 +74,7 @@ define([
     for (var i = 0; i < foo.data.length; ++i)
       expect(foo.data[i]).toBe(foo.data.length - i);
 
-    expect(foo.files.length).toBe(4);
-    for (var i = 0; i < foo.files.length; ++i)
-      expect(foo.files[i]).toBe(0xFFFF - i);
+    expect(foo.source).toBe(0xFFFF);
   }
 
   function ServiceImpl() {
diff --git a/mojo/public/system/core_cpp.h b/mojo/public/system/core_cpp.h
index 02ae4d5..3bc9349 100644
--- a/mojo/public/system/core_cpp.h
+++ b/mojo/public/system/core_cpp.h
@@ -25,6 +25,7 @@ class ScopedHandleBase {
 
  public:
   ScopedHandleBase() {}
+  explicit ScopedHandleBase(HandleType handle) : handle_(handle) {}
   ~ScopedHandleBase() { CloseIfNecessary(); }
 
   // Move-only constructor and operator=.
@@ -66,6 +67,11 @@ class ScopedHandleBase {
   HandleType handle_;
 };
 
+template <typename HandleType>
+inline ScopedHandleBase<HandleType> MakeScopedHandle(HandleType handle) {
+  return ScopedHandleBase<HandleType>(handle);
+}
+
 // Handle ----------------------------------------------------------------------
 
 const MojoHandle kInvalidHandleValue = MOJO_HANDLE_INVALID;
diff --git a/mojo/public/tests/bindings_connector_unittest.cc b/mojo/public/tests/bindings_connector_unittest.cc
index 10de52c..47052ab 100644
--- a/mojo/public/tests/bindings_connector_unittest.cc
+++ b/mojo/public/tests/bindings_connector_unittest.cc
@@ -210,6 +210,8 @@ TEST_F(BindingsConnectorTest, MessageWithHandles) {
   // TODO(vtl): Do we need a better way of "downcasting" the handle types?
   ScopedMessagePipeHandle smph;
   smph.reset(MessagePipeHandle(message_received.handles[0].value()));
+  message_received.handles[0] = Handle();  // |smph| now owns this handle.
+
   Connector connector_received(smph.Pass());
   Connector connector_original(handles[1].Pass());
 
diff --git a/mojo/public/tests/bindings_handle_passing_unittest.cc b/mojo/public/tests/bindings_handle_passing_unittest.cc
new file mode 100644
index 0000000..6ebc1bd
--- /dev/null
+++ b/mojo/public/tests/bindings_handle_passing_unittest.cc
@@ -0,0 +1,128 @@
+// Copyright 2013 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 "mojo/public/bindings/lib/remote_ptr.h"
+#include "mojo/public/tests/simple_bindings_support.h"
+#include "mojo/public/tests/test_support.h"
+#include "mojom/sample_factory.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace mojo {
+namespace test {
+namespace {
+
+const char kText1[] = "hello";
+const char kText2[] = "world";
+
+class SampleFactoryImpl : public sample::FactoryStub {
+ public:
+  explicit SampleFactoryImpl(ScopedMessagePipeHandle pipe)
+      : client_(pipe.Pass()) {
+    client_.SetPeer(this);
+  }
+
+  virtual void DoStuff(const sample::Request& request,
+                       ScopedMessagePipeHandle pipe) MOJO_OVERRIDE {
+    std::string text1;
+    EXPECT_TRUE(ReadTextMessage(pipe.get(), &text1));
+
+    std::string text2;
+    EXPECT_TRUE(ReadTextMessage(request.pipe().get(), &text2));
+
+    ScopedMessagePipeHandle pipe0;
+    CreateMessagePipe(&pipe0, &pipe1_);
+
+    EXPECT_TRUE(WriteTextMessage(pipe1_.get(), text2));
+
+    AllocationScope scope;
+    sample::Response::Builder response;
+    response.set_x(2);
+    response.set_pipe(pipe0.Pass());
+    client_->DidStuff(response.Finish(), text1);
+  }
+
+ private:
+  RemotePtr<sample::FactoryClient> client_;
+  ScopedMessagePipeHandle pipe1_;
+};
+
+class SampleFactoryClientImpl : public sample::FactoryClientStub {
+ public:
+  explicit SampleFactoryClientImpl(ScopedMessagePipeHandle pipe)
+      : factory_(pipe.Pass()),
+        got_response_(false) {
+    factory_.SetPeer(this);
+  }
+
+  void Start() {
+    ScopedMessagePipeHandle pipe0;
+    CreateMessagePipe(&pipe0, &pipe1_);
+
+    EXPECT_TRUE(WriteTextMessage(pipe1_.get(), kText1));
+
+    ScopedMessagePipeHandle pipe2;
+    CreateMessagePipe(&pipe2, &pipe3_);
+
+    EXPECT_TRUE(WriteTextMessage(pipe3_.get(), kText2));
+
+    AllocationScope scope;
+    sample::Request::Builder request;
+    request.set_x(1);
+    request.set_pipe(pipe2.Pass());
+    factory_->DoStuff(request.Finish(), pipe0.Pass());
+  }
+
+  bool got_response() const {
+    return got_response_;
+  }
+
+  virtual void DidStuff(const sample::Response& response,
+                        const String& text1) MOJO_OVERRIDE {
+    EXPECT_EQ(std::string(kText1), text1.To<std::string>());
+
+    std::string text2;
+    EXPECT_TRUE(ReadTextMessage(response.pipe().get(), &text2));
+    EXPECT_EQ(std::string(kText2), text2);
+
+    got_response_ = true;
+  }
+
+ private:
+  RemotePtr<sample::Factory> factory_;
+  ScopedMessagePipeHandle pipe1_;
+  ScopedMessagePipeHandle pipe3_;
+  bool got_response_;
+};
+
+}  // namespace
+
+class BindingsHandlePassingTest : public testing::Test {
+ public:
+  void PumpMessages() {
+    bindings_support_.Process();
+  }
+
+ private:
+  SimpleBindingsSupport bindings_support_;
+};
+
+TEST_F(BindingsHandlePassingTest, Basic) {
+  ScopedMessagePipeHandle pipe0;
+  ScopedMessagePipeHandle pipe1;
+  CreateMessagePipe(&pipe0, &pipe1);
+
+  SampleFactoryImpl factory(pipe0.Pass());
+  SampleFactoryClientImpl factory_client(pipe1.Pass());
+
+  factory_client.Start();
+
+  EXPECT_FALSE(factory_client.got_response());
+
+  PumpMessages();
+
+  EXPECT_TRUE(factory_client.got_response());
+}
+
+}  // namespace test
+}  // namespace mojo
diff --git a/mojo/public/tests/sample_factory.mojom b/mojo/public/tests/sample_factory.mojom
new file mode 100644
index 0000000..7ae6b34
--- /dev/null
+++ b/mojo/public/tests/sample_factory.mojom
@@ -0,0 +1,30 @@
+// Copyright 2013 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.
+
+module sample {
+
+// This sample shows how handles to MessagePipes can be sent as both parameters
+// to methods as well as fields on structs.
+
+struct Request {
+  int32 x;
+  handle<message_pipe> pipe;
+};
+
+struct Response {
+  int32 x;
+  handle<message_pipe> pipe;
+};
+
+[Peer=FactoryClient]
+interface Factory {
+  void DoStuff(Request request, handle<message_pipe> pipe);
+};
+
+[Peer=Factory]
+interface FactoryClient {
+  void DidStuff(Response response, string text);
+};
+
+}  // module sample
diff --git a/mojo/public/tests/test_support.cc b/mojo/public/tests/test_support.cc
index 151fae3..81a0c3a2 100644
--- a/mojo/public/tests/test_support.cc
+++ b/mojo/public/tests/test_support.cc
@@ -10,6 +10,53 @@
 namespace mojo {
 namespace test {
 
+bool WriteTextMessage(MessagePipeHandle handle, const std::string& text) {
+  MojoResult rv = WriteMessageRaw(handle,
+                                  text.data(),
+                                  static_cast<uint32_t>(text.size()),
+                                  NULL,
+                                  0,
+                                  MOJO_WRITE_MESSAGE_FLAG_NONE);
+  return rv == MOJO_RESULT_OK;
+}
+
+bool ReadTextMessage(MessagePipeHandle handle, std::string* text) {
+  MojoResult rv;
+  bool did_wait = false;
+
+  uint32_t num_bytes = 0, num_handles = 0;
+  for (;;) {
+    rv = ReadMessageRaw(handle,
+                        NULL,
+                        &num_bytes,
+                        NULL,
+                        &num_handles,
+                        MOJO_READ_MESSAGE_FLAG_NONE);
+    if (rv == MOJO_RESULT_NOT_FOUND) {
+      if (did_wait) {
+        assert(false);  // Looping endlessly!?
+        return false;
+      }
+      rv = Wait(handle, MOJO_WAIT_FLAG_READABLE, MOJO_DEADLINE_INDEFINITE);
+      if (rv != MOJO_RESULT_OK)
+        return false;
+      did_wait = true;
+    } else {
+      assert(!num_handles);
+      break;
+    }
+  }
+
+  text->resize(num_bytes);
+  rv = ReadMessageRaw(handle,
+                      &text->at(0),
+                      &num_bytes,
+                      NULL,
+                      &num_handles,
+                      MOJO_READ_MESSAGE_FLAG_NONE);
+  return rv == MOJO_RESULT_OK;
+}
+
 void IterateAndReportPerf(const char* test_name,
                           base::Callback<void()> single_iteration) {
   // TODO(vtl): These should be specifiable using command-line flags.
diff --git a/mojo/public/tests/test_support.h b/mojo/public/tests/test_support.h
index bddd7a0..9c144a3 100644
--- a/mojo/public/tests/test_support.h
+++ b/mojo/public/tests/test_support.h
@@ -5,11 +5,17 @@
 #ifndef MOJO_PUBLIC_TESTS_TEST_SUPPORT_H_
 #define MOJO_PUBLIC_TESTS_TEST_SUPPORT_H_
 
+#include <string>
+
 #include "base/callback.h"
+#include "mojo/public/system/core_cpp.h"
 
 namespace mojo {
 namespace test {
 
+bool WriteTextMessage(MessagePipeHandle handle, const std::string& text);
+bool ReadTextMessage(MessagePipeHandle handle, std::string* text);
+
 // Run |single_iteration| an appropriate number of times and report its
 // performance appropriately. (This actually runs |single_iteration| for a fixed
 // amount of time and reports the number of iterations per unit time.)
diff --git a/mojo/services/native_viewport/native_viewport.mojom b/mojo/services/native_viewport/native_viewport.mojom
index bd43b93..caae29a 100644
--- a/mojo/services/native_viewport/native_viewport.mojom
+++ b/mojo/services/native_viewport/native_viewport.mojom
@@ -8,7 +8,7 @@ module mojo {
 interface NativeViewport {
   void Open();
   void Close();
-  void CreateGLES2Context(handle gles2_client);
+  void CreateGLES2Context(handle<message_pipe> gles2_client);
 };
 
 [Peer=NativeViewport]
diff --git a/mojo/services/native_viewport/native_viewport_impl.cc b/mojo/services/native_viewport/native_viewport_impl.cc
index 80c1afa..bce78e3 100644
--- a/mojo/services/native_viewport/native_viewport_impl.cc
+++ b/mojo/services/native_viewport/native_viewport_impl.cc
@@ -35,10 +35,9 @@ void NativeViewportImpl::Close() {
   native_viewport_->Close();
 }
 
-void NativeViewportImpl::CreateGLES2Context(mojo::Handle gles2_client) {
-  ScopedMessagePipeHandle handle;
-  handle.reset(MessagePipeHandle(gles2_client.value()));
-  gles2_.reset(new GLES2Impl(handle.Pass()));
+void NativeViewportImpl::CreateGLES2Context(
+    ScopedMessagePipeHandle gles2_client) {
+  gles2_.reset(new GLES2Impl(gles2_client.Pass()));
   CreateGLES2ContextIfNeeded();
 }
 
diff --git a/mojo/services/native_viewport/native_viewport_impl.h b/mojo/services/native_viewport/native_viewport_impl.h
index 9a90d91..332105e 100644
--- a/mojo/services/native_viewport/native_viewport_impl.h
+++ b/mojo/services/native_viewport/native_viewport_impl.h
@@ -29,7 +29,8 @@ class NativeViewportImpl : public NativeViewportStub,
 
   virtual void Open() OVERRIDE;
   virtual void Close() OVERRIDE;
-  virtual void CreateGLES2Context(mojo::Handle gles2_client) OVERRIDE;
+  virtual void CreateGLES2Context(
+      ScopedMessagePipeHandle gles2_client) OVERRIDE;
 
  private:
   // Overridden from services::NativeViewportDelegate: