Create ResourceProgressEvent, expose as Chromium API

Source/WebKit/chromium/src/WebDOMEvent.cpp

Index: Source/WebKit/chromium/src/WebDOMEvent.cpp
diff --git a/Source/WebKit/chromium/src/WebDOMEvent.cpp b/Source/WebKit/chromium/src/WebDOMEvent.cpp
index f72170cfa7eaba433ee127f0ee941985b5a965ec..d5fd463d7efc5c313b7b8db75178a6f29c56ee54 100644
--- a/Source/WebKit/chromium/src/WebDOMEvent.cpp
+++ b/Source/WebKit/chromium/src/WebDOMEvent.cpp
@@ -56,12 +56,17 @@ void WebDOMEvent::assign(const WebDOMEvent& other)
     assign(p);
 }
 
-void WebDOMEvent::assign(WebDOMEventPrivate* p)
+void WebDOMEvent::assign(WebDOMEventPrivate* event)
 {
-    // p is already ref'd for us by the caller
+    // event is already ref'd for us by the caller
     if (m_private)
         m_private->deref();

[abarth-chromium, 2013/05/20 21:16:32]

Ouch.  We should remove this function.  It's asking for a use-after-free.

[dmichael (off chromium), 2013/05/23 16:47:00]

Good point, I fixed it in a separate CL:
https://codereview.chromium.org/15271012/

-    m_private = p;
+    m_private = event;
+}
+
+void WebDOMEvent::assign(const WTF::PassRefPtr<WebDOMEventPrivate>& event)
+{
+    assign(event.leakRef());

[abarth-chromium, 2013/05/20 21:16:32]

Can't we just assign m_private directly?  The raw version of this function is
bad news bears.

[dmichael (off chromium), 2013/05/23 16:47:00]

Done.

 }
 
 WebDOMEvent::WebDOMEvent(const WTF::PassRefPtr<WebCore::Event>& event)