Add TargetIsPing and have PingLoader use it.

Add TargetIsPing and have PingLoader use it.

We'll use it to detach requests from renderers. This is used both for
PingLoader::loadImage and PingLoader::sendPing. Temporarily define a
WEBKIT_HAS_TARGET_IS_PING preprocessor symbol until Chromium downstream
is updated.

(Even though the former comes from loading an image, it's part of the
special-case behavior where images loaded in unload handlers don't get
cancelled, and doesn't load like a normal image, so we shouldn't be treating it
as one.)

BUG=302816
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=162565

[davidben, 2013-10-31 22:50:18]

Actually, better plan, based on how ResourceType::XHR was added. This shouldn't
land until a preparatory Chromium CL and will look different.

1. Chromium CL to define ResourceType::PING and consume TargetIsPing #ifdef'd on
WEBKIT_HAS_TARGET_IS_PING symbol.
2. This CL, but without the map-back-to-subresource hack and defining the
preprocessor symbol.
--- wait for Blink roll ---
3. Chromium CL to remove the #ifdef and hook ResourceType::PING to the machinery
added for ResourceType::PREFETCH. Everything works.
4. Blink CL to remove the #define.

This way I only wait on one Blink roll, rather than two.

[abarth-chromium, 2013-11-01 17:05:41]

LGTM

[davidben, 2013-11-22 21:01:59]

On 2013/11/01 17:05:41, abarth wrote:
> LGTM

https://codereview.chromium.org/55513002/ and the (re-)land of its prerequisite
finally landed, so I'll go submit this to the queue.

[commit-bot: I haz the power, 2013-11-22 21:02:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/davidben@chromium.org/55203003/110001

[commit-bot: I haz the power, 2013-11-22 22:26:32]

Change committed as 162565