Use toDocument instead of static_cast<Document*>.

Source/WebKit/chromium/src/DatabaseObserver.cpp

Index: Source/WebKit/chromium/src/DatabaseObserver.cpp
diff --git a/Source/WebKit/chromium/src/DatabaseObserver.cpp b/Source/WebKit/chromium/src/DatabaseObserver.cpp
index fe02671cb4f24e007118bb24cabcf1f23d3bd666..7d4dfb96c52f78a835942e6c9ddf77ab781f4bd5 100644
--- a/Source/WebKit/chromium/src/DatabaseObserver.cpp
+++ b/Source/WebKit/chromium/src/DatabaseObserver.cpp
@@ -133,7 +133,7 @@ bool DatabaseObserver::canEstablishDatabase(ScriptExecutionContext* scriptExecut
     ASSERT(scriptExecutionContext->isContextThread());
     ASSERT(scriptExecutionContext->isDocument() || scriptExecutionContext->isWorkerGlobalScope());
     if (scriptExecutionContext->isDocument()) {
-        Document* document = static_cast<Document*>(scriptExecutionContext);
+        Document* document = toDocument(scriptExecutionContext);
         WebFrameImpl* webFrame = WebFrameImpl::fromFrame(document->frame());
         if (!webFrame)
             return false;