Implements JS bindings for mojo shared buffer.

third_party/WebKit/Source/core/mojo/MojoHandle.idl

Index: third_party/WebKit/Source/core/mojo/MojoHandle.idl
diff --git a/third_party/WebKit/Source/core/mojo/MojoHandle.idl b/third_party/WebKit/Source/core/mojo/MojoHandle.idl
index 34b1dfc97eec0b9fdfba22eb17b66a65d9ac1fdb..ce9aedd6ef0282334e3b8b4e6e033098c615e10b 100644
--- a/third_party/WebKit/Source/core/mojo/MojoHandle.idl
+++ b/third_party/WebKit/Source/core/mojo/MojoHandle.idl
@@ -9,6 +9,13 @@ callback MojoWatchCallback = void (MojoResult result);
 ] interface MojoHandle {
     void close();
     [CallWith=ScriptState] MojoWatcher watch(MojoHandleSignals signals, MojoWatchCallback callback);
+
+    // TODO(alokp): Create MessagePipeHandle, a subclass of MojoHandle
+    // and move the following member functions.
     MojoResult writeMessage(BufferSource buffer, sequence<MojoHandle> handles);
     MojoReadMessageResult readMessage(optional MojoReadMessageFlags flags);
+
+    // TODO(alokp): Create SharedBufferHandle, a subclass of MojoHandle
+    // and move the following member functions.
+    MojoMapBufferResult mapBuffer(unsigned long offset, unsigned long numBytes);
 };