Use null Strings for default values of MessageEvent properties

Use null Strings for default values of MessageEvent properties

Use null Strings for default values of MessageEvent properties instead of empty
ones. Null strings are cheaper to construct and there is no web-exposed behavior
change since a null String is exposed as an empty one on JS side.

This change is based on WebKit r155959.

R=haraken
TEST=fast/events/constructors/message-event-constructor.html
BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=158113

[haraken, 2013-09-19 00:41:01]

> since a null String is exposed as an empty one on JS side.

This would depend on how [TreatReturnedNullStringAs=...] is described in IDL
files. However, in the particular case in your CL, there is no web-exposed
change.

LGTM.

https://codereview.chromium.org/23591059/diff/1/Source/core/workers/SharedWor...
File Source/core/workers/SharedWorkerGlobalScope.cpp (right):

https://codereview.chromium.org/23591059/diff/1/Source/core/workers/SharedWor...
Source/core/workers/SharedWorkerGlobalScope.cpp:49: RefPtr<MessageEvent> event =
MessageEvent::create(adoptPtr(new MessagePortArray(1, port)), String(),
String(), port);

You can write:

  PassRefPtr<MessageEvent> createConnectEvent(PassRefPtr<MessagePort> port) {
    RefPtr<MessageEvent> event = MessageEvent::create(adoptPtr(new
MessagePortArray(1, port)), String(), String(), port);
    ...;
  }

[commit-bot: I haz the power, 2013-09-20 09:53:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@sisa.samsung.com/23591059/2001

[commit-bot: I haz the power, 2013-09-20 11:22:43]

Retried try job too often on mac_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_blink_...

[do-not-use, 2013-09-20 12:43:34]

https://codereview.chromium.org/23591059/diff/1/Source/core/workers/SharedWor...
File Source/core/workers/SharedWorkerGlobalScope.cpp (right):

https://codereview.chromium.org/23591059/diff/1/Source/core/workers/SharedWor...
Source/core/workers/SharedWorkerGlobalScope.cpp:49: RefPtr<MessageEvent> event =
MessageEvent::create(adoptPtr(new MessagePortArray(1, port)), String(),
String(), port);
On 2013/09/19 00:41:02, haraken wrote:
> 
> You can write:
> 
>   PassRefPtr<MessageEvent> createConnectEvent(PassRefPtr<MessagePort> port) {
>     RefPtr<MessageEvent> event = MessageEvent::create(adoptPtr(new
> MessagePortArray(1, port)), String(), String(), port);
>     ...;
>   }

This does not work. I have just tried to confirm.
fast/workers/shared-worker-messageevent-source.html times out.

I assume one of the 2 ports gets nullified.

[commit-bot: I haz the power, 2013-09-20 12:44:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@sisa.samsung.com/23591059/23001

[commit-bot: I haz the power, 2013-09-20 13:38:05]

Change committed as 158113