Don't serialize extension user script injection results unless the extension

Don't serialize extension user script injection results unless the extension
actually cares about the result. Times it might not care: if it's a content
script injected declaratively, or if it doesn't give a result callback.

BUG=269916
R=mpcomplete@chromium.org
TBR=cdn@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=219908

[not at google - send to devlin, 2013-08-23 00:25:40]

Same bug, but this one doesn't break incompatibility in any way, but also
doesn't cover all cases. It does fix some pretty severe wastage in content
script injection in any case.

[not at google - send to devlin, 2013-08-23 01:19:13]

https://codereview.chromium.org/22875046/diff/1/chrome/renderer/extensions/ch...
File chrome/renderer/extensions/chrome_v8_context_set.h (right):

https://codereview.chromium.org/22875046/diff/1/chrome/renderer/extensions/ch...
chrome/renderer/extensions/chrome_v8_context_set.h:71: ChromeV8Context*
GetByWebFrame(WebKit::WebFrame* web_frame) const;
Ok this method doesn't make any sense. There are multiple contexts per frame.
Don't know what I was thinking. Will fix tomorrow.

[Matt Perry, 2013-08-23 18:54:09]

lgtm

[not at google - send to devlin, 2013-08-23 20:18:23]

+cdn for extension messages

[commit-bot: I haz the power, 2013-08-27 15:36:10]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/kalman@chromium.org/22875046/20001

[Cris Neckar, 2013-08-27 17:20:34]

IPC changes lgtm

[commit-bot: I haz the power, 2013-08-28 00:40:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/kalman@chromium.org/22875046/20001

[commit-bot: I haz the power, 2013-08-28 04:08:43]

Change committed as 219908