[Mac] Defer loading the Web Inspector bundle until it's necessary.
<http://webkit.org/b/107999>
<rdar://problem/13091861>

Reviewed by Anders Carlsson.

Don't instantiate an NSBundle for the Web Inspector before it's needed.
1.51MB progression on Membuster3.

* WebProcess/WebPage/WebInspector.cpp:
(WebKit::WebInspector::WebInspector):
* WebProcess/WebPage/WebInspector.h:
(WebInspector):
* WebProcess/WebPage/mac/WebInspectorMac.mm:
(WebKit::WebInspector::setInspectorUsesWebKitUserInterface):
(WebKit::WebInspector::localizedStringsURL):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140903 268f45cc-cd09-0410-ab3c-d52691b4dbfc