Bug 1599801 - NullPrincipal::Init is infallible. r=bzbarsky

I also cleaned up the comment a bit.

Differential Revision: https://phabricator.services.mozilla.com/D54970

caps/NullPrincipal.cpp

@@ -54,8 +54,7 @@ already_AddRefed<NullPrincipal> NullPrincipal::CreateWithInheritedAttributes(
 already_AddRefed<NullPrincipal> NullPrincipal::CreateWithInheritedAttributes(
     const OriginAttributes& aOriginAttributes, bool aIsFirstParty) {
   RefPtr<NullPrincipal> nullPrin = new NullPrincipal();
-  nsresult rv = nullPrin->Init(aOriginAttributes, aIsFirstParty);
-  MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv));
+  nullPrin->Init(aOriginAttributes, aIsFirstParty);
   return nullPrin.forget();
 }
 
@@ -98,8 +97,8 @@ nsresult NullPrincipal::Init(const OriginAttributes& aOriginAttributes,
   return NS_OK;
 }
 
-nsresult NullPrincipal::Init(const OriginAttributes& aOriginAttributes,
-                             bool aIsFirstParty) {
+void NullPrincipal::Init(const OriginAttributes& aOriginAttributes,
+                         bool aIsFirstParty) {
   mURI = new NullPrincipalURI();
 
   nsAutoCString originNoSuffix;
@@ -119,8 +118,6 @@ nsresult NullPrincipal::Init(const OriginAttributes& aOriginAttributes,
   }
 
   FinishInit(originNoSuffix, attrs);
-
-  return NS_OK;
 }
 
 nsresult NullPrincipal::GetScriptLocation(nsACString& aStr) {

caps/NullPrincipal.h

@@ -112,11 +112,11 @@ class NullPrincipal final : public BasePrincipal {
   nsCOMPtr<nsIURI> mURI;
 
  private:
-  // If aIsFirstParty is true, this NullPrincipal will be initialized base on
-  // the aOriginAttributes with FirstPartyDomain set to an unique value, and
-  // this value is generated from mURI.path, with ".mozilla" appending at the
+  // If aIsFirstParty is true, this NullPrincipal will be initialized based on
+  // the aOriginAttributes with FirstPartyDomain set to a unique value.
+  // This value is generated from mURI.path, with ".mozilla" appended at the
   // end.
-  nsresult Init(const OriginAttributes& aOriginAttributes, bool aIsFirstParty);
+  void Init(const OriginAttributes& aOriginAttributes, bool aIsFirstParty);
 };
 
 }  // namespace mozilla