Bug 1243849 - Restore support for accessing the Cache API from app:// URLs and also for storing requests/responses with app:// URLs within it; r=bkelly

Firefox OS still needs to use the cache API both to access it, and possibly
store app:// URL resources inside it.  See for example code in
https://github.com/fxos-components/fxos-fastlist/blob/master/fxos-fastlist.js
that manipulates the cache.  Let's restore this support for now since it's
pretty harmless.

dom/cache/CacheStorage.cpp

@@ -119,6 +119,7 @@ IsTrusted(const PrincipalInfo& aPrincipalInfo, bool aTestingPrefEnabled)
 
   nsAutoCString scheme(Substring(flatURL, schemePos, schemeLen));
   if (scheme.LowerCaseEqualsLiteral("https") ||
+      scheme.LowerCaseEqualsLiteral("app") ||
       scheme.LowerCaseEqualsLiteral("file")) {
     return true;
   }

dom/cache/TypeUtils.cpp

@@ -417,7 +417,8 @@ TypeUtils::ProcessURL(nsACString& aUrl, bool* aSchemeValidOut,
   if (aSchemeValidOut) {
     nsAutoCString scheme(Substring(flatURL, schemePos, schemeLen));
     *aSchemeValidOut = scheme.LowerCaseEqualsLiteral("http") ||
-                       scheme.LowerCaseEqualsLiteral("https");
+                       scheme.LowerCaseEqualsLiteral("https") ||
+                       scheme.LowerCaseEqualsLiteral("app");
   }
 
   uint32_t queryPos;