Bug 1335890 - Factor out nsContentUtils::SubjectPrincipal version that takes JSContext r=bz

MozReview-Commit-ID: CGRipgKUm7g

--HG--
extra : rebase_source : 33c2dbd7eaad80a3e523113aa8217ba1e086572a

dom/base/nsContentUtils.cpp

@@ -2084,11 +2084,8 @@ nsContentUtils::CallerHasPermission(JSContext* aCx, const nsAString& aPerm)
     return true;
   }
 
-  JSCompartment* c = js::GetContextCompartment(aCx);
-  nsIPrincipal* p = nsJSPrincipals::get(JS_GetCompartmentPrincipals(c));
-
   // Otherwise, only allow if caller is an addon with the permission.
-  return BasePrincipal::Cast(p)->AddonHasPermission(aPerm);
+  return BasePrincipal::Cast(SubjectPrincipal(aCx))->AddonHasPermission(aPerm);
 }
 
 //static
@@ -2174,16 +2171,8 @@ nsContentUtils::IsCallerContentXBL()
 bool
 nsContentUtils::IsSystemCaller(JSContext* aCx)
 {
-  MOZ_ASSERT(NS_IsMainThread());
-
-  // This is similar to what SubjectPrincipal() does, except we do in fact
-  // assume that we're in a compartment here; anyone who calls this function in
-  // situations where that's not the case is doing it wrong.
-  JSCompartment *compartment = js::GetContextCompartment(aCx);
-  MOZ_ASSERT(compartment);
-
-  JSPrincipals *principals = JS_GetCompartmentPrincipals(compartment);
-  return nsJSPrincipals::get(principals) == sSystemPrincipal;
+  // Note that SubjectPrincipal() assumes we are in a compartment here.
+  return SubjectPrincipal(aCx) == sSystemPrincipal;
 }
 
 bool
@@ -2777,6 +2766,22 @@ nsContentUtils::GenerateStateKey(nsIContent* aContent,
   return NS_OK;
 }
 
+// static
+nsIPrincipal*
+nsContentUtils::SubjectPrincipal(JSContext* aCx)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // As opposed to SubjectPrincipal(), we do in fact assume that
+  // we're in a compartment here; anyone who calls this function
+  // in situations where that's not the case is doing it wrong.
+  JSCompartment* compartment = js::GetContextCompartment(aCx);
+  MOZ_ASSERT(compartment);
+
+  JSPrincipals* principals = JS_GetCompartmentPrincipals(compartment);
+  return nsJSPrincipals::get(principals);
+}
+
 // static
 nsIPrincipal*
 nsContentUtils::SubjectPrincipal()
@@ -2803,7 +2808,7 @@ nsContentUtils::SubjectPrincipal()
   // The natural thing to return is a null principal. Ideally, we'd return a
   // different null principal each time, to avoid any unexpected interactions
   // when the principal accidentally gets inherited somewhere. But
-  // GetSubjectPrincipal doesn't return strong references, so there's no way to
+  // SubjectPrincipal doesn't return strong references, so there's no way to
   // sanely manage the lifetime of multiple null principals.
   //
   // So we use a singleton null principal. To avoid it being accidentally
@@ -2814,8 +2819,7 @@ nsContentUtils::SubjectPrincipal()
     return sNullSubjectPrincipal;
   }
 
-  JSPrincipals *principals = JS_GetCompartmentPrincipals(compartment);
-  return nsJSPrincipals::get(principals);
+  return SubjectPrincipal(cx);
 }
 
 // static

dom/base/nsContentUtils.h

@@ -545,6 +545,10 @@ public:
     return sSecurityManager;
   }
 
+  // Returns the subject principal from the JSContext. May only be called
+  // from the main thread and assumes an existing compartment.
+  static nsIPrincipal* SubjectPrincipal(JSContext* aCx);
+
   // Returns the subject principal. Guaranteed to return non-null. May only
   // be called when nsContentUtils is initialized.
   static nsIPrincipal* SubjectPrincipal();