<iframe> should expose its mojo::ServiceProvider handle

<iframe> should expose its mojo::ServiceProvider handle

After this CL, you can exchange services with the app loaded in the iframe by
calling takeServiceProvider() on the iframe element. That gives you the raw
handle, which you'll need to wrap in the appropriate mojom-generated interface.

R=hansmuller@google.com, sky@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/b489eb1bbbc5c46602bbeb7a1477c4d6af7078a8

[hans, 2015-01-21 21:08:50]

hans@chromium.org changed reviewers:
+ hans@chromium.org

[hans, 2015-01-21 21:08:51]

s/hans/hansmuller/, just guessing :)

[abarth-chromium, 2015-01-21 21:33:01]

On 2015/01/21 at 21:08:51, hans wrote:
> s/hans/hansmuller/, just guessing :)

Sorry.  :(

[abarth-chromium, 2015-01-21 21:33:11]

abarth@chromium.org changed reviewers:
+ hansmuller@chromium.org
- hans@chromium.org

[hansmuller1, 2015-01-21 22:38:06]

hansmuller@google.com changed reviewers:
+ hansmuller@google.com

[hansmuller1, 2015-01-21 22:38:07]

This LGTM. I assume that takeFoo() is a convention that implies that the
function can only be called once.  A DCHECK warning might be helpful.

[abarth-chromium, 2015-01-22 00:18:33]

On 2015/01/21 at 22:38:07, hansmuller wrote:
> This LGTM. I assume that takeFoo() is a convention that implies that the
function can only be called once.  A DCHECK warning might be helpful.

You can call it again.  It will just give you back an invalid handle.

[abarth-chromium, 2015-01-22 00:25:02]

Committed patchset #1 (id:1) manually as
b489eb1bbbc5c46602bbeb7a1477c4d6af7078a8 (presubmit successful).