Bug 1517241 - Rename nsIDocument to mozilla::dom::Document. r=smaug

Summary: Really sorry for the size of the patch. It's mostly automatic
s/nsIDocument/Document/ but I had to fix up in a bunch of places manually to
add the right namespacing and such.

Overall it's not a very interesting patch I think.

nsDocument.cpp turns into Document.cpp, nsIDocument.h into Document.h and
nsIDocumentInlines.h into DocumentInlines.h.

I also changed a bunch of nsCOMPtr usage to RefPtr, but not all of it.

While fixing up some of the bits I also removed some unneeded OwnerDoc() null
checks and such, but I didn't do anything riskier than that.

dom/html/HTMLButtonElement.cpp

@@ -18,7 +18,7 @@
 #include "nsIURL.h"
 #include "nsIFrame.h"
 #include "nsIFormControlFrame.h"
-#include "nsIDocument.h"
+#include "mozilla/dom/Document.h"
 #include "mozilla/ContentEvents.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventStateManager.h"
@@ -289,8 +289,7 @@ nsresult HTMLButtonElement::PostHandleEvent(EventChainPostVisitor& aVisitor) {
   return rv;
 }
 
-nsresult HTMLButtonElement::BindToTree(nsIDocument* aDocument,
-                                       nsIContent* aParent,
+nsresult HTMLButtonElement::BindToTree(Document* aDocument, nsIContent* aParent,
                                        nsIContent* aBindingParent) {
   nsresult rv = nsGenericHTMLFormElementWithState::BindToTree(
       aDocument, aParent, aBindingParent);