Add a Setting to make iframes load at VeryLow priority, disabled by default.

Source/web/WebSettingsImpl.cpp

Index: Source/web/WebSettingsImpl.cpp
diff --git a/Source/web/WebSettingsImpl.cpp b/Source/web/WebSettingsImpl.cpp
index be93bb613e1dcecfb14b90261f71ab2f75d2c051..e1cf083d8cfe7185657661500186a5738e8e89d8 100644
--- a/Source/web/WebSettingsImpl.cpp
+++ b/Source/web/WebSettingsImpl.cpp
@@ -374,6 +374,11 @@ void WebSettingsImpl::setXSSAuditorEnabled(bool enabled)
     m_settings->setXSSAuditorEnabled(enabled);
 }
 
+void WebSettingsImpl::setLowPriorityIframes(bool enabled)
+{
+    m_settings->setLowPriorityIframes(enabled);
+}
+
 void WebSettingsImpl::setTextTrackBackgroundColor(const WebString& color)
 {
     m_settings->setTextTrackBackgroundColor(color);