Bug 1323987 - Add about:printpreview redirector. r=mconley

This patch adds a new entry for "about:printpreview" in nsAboutRedirector.
We also make sure the URI is maintained when redirecting.

MozReview-Commit-ID: 3LlyNJqKOhZ

--HG--
extra : rebase_source : 669129e51e894910f5b7f06a3226699afc580abf

docshell/base/nsAboutRedirector.cpp

@@ -138,6 +138,12 @@ static RedirEntry kRedirMap[] = {
   {
     "webrtc", "chrome://global/content/aboutwebrtc/aboutWebrtc.html",
     nsIAboutModule::ALLOW_SCRIPT
+  },
+  {
+    "printpreview", "about:blank",
+    nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
+    nsIAboutModule::HIDE_FROM_ABOUTABOUT |
+    nsIAboutModule::URI_CAN_LOAD_IN_CHILD
   }
 };
 static const int kRedirTotal = mozilla::ArrayLength(kRedirMap);
@@ -173,9 +179,11 @@ nsAboutRedirector::NewChannel(nsIURI* aURI,
                                &isUIResource);
       NS_ENSURE_SUCCESS(rv, rv);
 
-      nsLoadFlags loadFlags =
-        isUIResource ? static_cast<nsLoadFlags>(nsIChannel::LOAD_NORMAL)
-                     : static_cast<nsLoadFlags>(nsIChannel::LOAD_REPLACE);
+      bool isAboutBlank = NS_IsAboutBlank(tempURI);
+
+      nsLoadFlags loadFlags = isUIResource || isAboutBlank
+                    ? static_cast<nsLoadFlags>(nsIChannel::LOAD_NORMAL)
+                    : static_cast<nsLoadFlags>(nsIChannel::LOAD_REPLACE);
 
       rv = NS_NewChannelInternal(getter_AddRefs(tempChannel),
                                  tempURI,

docshell/build/nsDocShellModule.cpp

@@ -189,6 +189,7 @@ const mozilla::Module::ContractIDEntry kDocShellContracts[] = {
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "support", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "telemetry", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_ABOUT_MODULE_CONTRACTID_PREFIX "webrtc", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
+  { NS_ABOUT_MODULE_CONTRACTID_PREFIX "printpreview", &kNS_ABOUT_REDIRECTOR_MODULE_CID },
   { NS_URI_LOADER_CONTRACTID, &kNS_URI_LOADER_CID },
   { NS_DOCUMENTLOADER_SERVICE_CONTRACTID, &kNS_DOCUMENTLOADER_SERVICE_CID },
   { NS_HANDLERSERVICE_CONTRACTID, &kNS_CONTENTHANDLERSERVICE_CID, mozilla::Module::CONTENT_PROCESS_ONLY },