for the existence of a PluginHalterDelegate.

This fixes a leak of WebPluginHalterClients:
https://bugs.webkit.org/show_bug.cgi?id=30119.

WebCore:

Reviewed by Dan Bernstein.

* WebCore.base.exp:
Removed the export of WebCore::Settings::setPluginHalterEnabled().

* loader/EmptyClients.h:
(WebCore::EmptyPluginHalterClient::enabled):

* page/Page.cpp:
(WebCore::Page::Page):
Remove initialization of m_pluginHalterClient, which was removed. If a
non-null PluginHalterClient was passed, create the PluginHalter, and
set its allowed run time.

* page/Page.h:
Removed pluginHalterEnabledStateChanged() and m_pluginHalterClient.

* page/PluginHalter.cpp:
(WebCore::PluginHalter::didStartPlugin):
Check whether the PluginHalterClient is enabled.
(WebCore::PluginHalter::didStopPlugin):
Ditto.

* page/PluginHalter.h:
Made m_client an OwnPtr.

* page/PluginHalterClient.h:
Added a function to return the enabled state.

* page/Settings.cpp:
(WebCore::Settings::Settings):
Remove initialization of removed member.

* page/Settings.h:
Removed settings for the enabled state of the PluginHalter; we now use
the existence of a WebPluginHalterDelegate to determine whether the
PluginHalter is enabled.

WebKit/mac:

* WebCoreSupport/WebPluginHalterClient.h:
Add declaration for new function.

* WebCoreSupport/WebPluginHalterClient.mm:
(WebPluginHalterClient::enabled):
Check whether the UIDelegate responds to shouldHaltPlugin.

* WebView/WebPreferenceKeysPrivate.h:
Remove the "enabled" preference key.

* WebView/WebPreferences.mm:
(+[WebPreferences initialize]):
Remove the initialization of the pref.

* WebView/WebPreferencesPrivate.h:
Remove the getter/setter for this pref.

* WebView/WebView.mm:
(-[WebView _preferencesChangedNotification:]):
Remove propagation of the pref.

WebKit/win:

* Interfaces/IWebPreferencesPrivate.idl:
Remove the getter and setter.

* WebCoreSupport/WebPluginHalterClient.cpp:
(WebPluginHalterClient::enabled):
Return true if the delegate exists.

* WebCoreSupport/WebPluginHalterClient.h:
Declare implementation of enabled().

* WebPreferenceKeysPrivate.h:
Removed the pref key.

* WebPreferences.cpp:
(WebPreferences::initializeDefaultSettings):
Removed initialization of the pref.

* WebPreferences.h:
Removed declaration of the getter/setter.

* WebView.cpp:
(WebView::notifyPreferencesChanged):
Don't propagate the pref.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@49385 268f45cc-cd09-0410-ab3c-d52691b4dbfc