Move plug-in enumeration back to the main thread
https://bugs.webkit.org/show_bug.cgi?id=109337
<rdar://problem/12015046>

Reviewed by Andreas Kling.

Plug-in enumeration was moved to a separate work queue to improve responsiveness, but
doing so lead to crashes when WebKit1 would enumerate plug-ins on the main thread at the same time.
Bug <rdar://problem/13185819> tracks fixing the responsiveness issue by spawning a plug-in process
and have it do the enumeration.

* Shared/Plugins/Netscape/mac/NetscapePluginModuleMac.mm:
(WebKit::getPluginInfoFromCarbonResources):
* UIProcess/WebProcessProxy.cpp:
(WebKit::WebProcessProxy::connectionWillOpen):
(WebKit::WebProcessProxy::connectionWillClose):
(WebKit::WebProcessProxy::getPlugins):
* UIProcess/WebProcessProxy.h:
(WebCore):
(WebProcessProxy):
* UIProcess/WebProcessProxy.messages.in:
* WebProcess/WebCoreSupport/WebPlatformStrategies.cpp:
(WebKit):
(WebKit::WebPlatformStrategies::populatePluginCache):
* WebProcess/WebProcess.cpp:
* WebProcess/WebProcess.h:
(WebProcess):
* WebProcess/WebProcess.messages.in:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142339 268f45cc-cd09-0410-ab3c-d52691b4dbfc