Bug 1274415 - Fix -Wshadow warnings in caps/ directory. r=dveditz

caps/BasePrincipal.cpp:562:28 [-Wshadow] declaration shadows a local variable
caps/nsScriptSecurityManager.cpp:675:18 [-Wshadow] declaration shadows a local variable
caps/nsScriptSecurityManager.cpp:854:14 [-Wshadow] declaration shadows a local variable

caps/BasePrincipal.cpp

@@ -551,7 +551,6 @@ BasePrincipal::CreateCodebasePrincipal(nsIURI* aURI, const PrincipalOriginAttrib
   bool inheritsPrincipal;
   nsresult rv = NS_URIChainHasFlags(aURI, nsIProtocolHandler::URI_INHERITS_SECURITY_CONTEXT,
                                     &inheritsPrincipal);
-  nsCOMPtr<nsIPrincipal> principal;
   if (NS_FAILED(rv) || inheritsPrincipal) {
     return nsNullPrincipal::Create(aAttrs);
   }

caps/moz.build

@@ -60,6 +60,3 @@ if CONFIG['ENABLE_TESTS']:
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
-
-if CONFIG['GNU_CXX']:
-    CXXFLAGS += ['-Wno-error=shadow']

caps/nsScriptSecurityManager.cpp

@@ -672,7 +672,7 @@ EqualOrSubdomain(nsIURI* aProbeArg, nsIURI* aBase)
         }
 
         nsAutoCString host, newHost;
-        nsresult rv = probe->GetHost(host);
+        rv = probe->GetHost(host);
         NS_ENSURE_SUCCESS(rv, false);
 
         rv = tldService->GetNextSubDomain(host, newHost);
@@ -850,8 +850,6 @@ nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
         // as long as they don't represent null principals...
         // Or they don't require an special permission to do so
         // See bug#773886
-
-        bool hasFlags;
         rv = NS_URIChainHasFlags(targetBaseURI,
                                  nsIProtocolHandler::URI_CROSS_ORIGIN_NEEDS_WEBAPPS_PERM,
                                  &hasFlags);