[Mojo] Improve JavaScript API for MojoReadMessage

[Mojo] Improve JavaScript API for MojoReadMessage

Originally, I tried to make the JavaScript bindings for the core Mojo APIs a
literal translation of the C APIs, but that makes MojoReadMessage a bit awkward
because C needs to worry much more about buffer allocation than JavaScript. In
building towards using the hello_world_service, I found that it was much easier
to push the MojoReadMessage pattern from connector.cc into C++ and make the
JavaScript API a bit more idiomatic by just returning an ArrayBuffer for the
message and an Array of handles.

BUG=317398
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=236999

[abarth-chromium, 2013-11-22 09:35:25]

https://codereview.chromium.org/83143002/diff/1/mojo/public/bindings/mojom_bi...
File mojo/public/bindings/mojom_bindings_generator.gypi (right):

https://codereview.chromium.org/83143002/diff/1/mojo/public/bindings/mojom_bi...
mojo/public/bindings/mojom_bindings_generator.gypi:34:
'<(output_dir)/<(RULE_INPUT_ROOT).js',
This change is a bit unrelated to the rest of the CL.  I could split it off, but
it seemed trivial.

[abarth-chromium, 2013-11-23 17:17:28]

This CL is ready for review.  PTAL.  Thanks!

[darin (slow to review), 2013-11-23 19:20:01]

LGTM

[commit-bot: I haz the power, 2013-11-23 19:26:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/83143002/1

[commit-bot: I haz the power, 2013-11-23 19:38:35]

Retried try job too often on linux_rel for step(s) base_unittests,
browser_tests, interactive_ui_tests, net_unittests, unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_rel&...

[commit-bot: I haz the power, 2013-11-23 20:31:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/83143002/1

[commit-bot: I haz the power, 2013-11-23 21:09:38]

Retried try job too often on linux_rel for step(s) base_unittests,
browser_tests, cacheinvalidation_unittests, cc_unittests, check_deps,
chromedriver2_unittests, components_unittests, content_browsertests,
content_unittests, crypto_unittests, google_apis_unittests, gpu_unittests,
interactive_ui_tests, ipc_tests, jingle_unittests, media_unittests,
nacl_integration, net_unittests, ppapi_unittests, printing_unittests,
remoting_unittests, sandbox_linux_unittests, sql_unittests,
sync_integration_tests, sync_unit_tests, unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_rel&...

[commit-bot: I haz the power, 2013-11-23 21:35:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/83143002/340001

[commit-bot: I haz the power, 2013-11-24 19:10:13]

Change committed as 236999