HostResolverImpl will return ERR_NAME_NOT_RESOLVED instead of Ok if address list is empty

BUG=224248

TEST=net_unittests --gtest_filter=HostResolverImplTest.EmptyListMeansNameNotResolved
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/14760008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@198799 0039d316-1c4b-4281-b951-d872f2087c98

net/dns/host_resolver_impl.cc

@@ -682,7 +682,11 @@ class HostResolverImpl::ProcTask
                         int error,
                         const int os_error) {
     DCHECK(origin_loop_->BelongsToCurrentThread());
-    DCHECK(error || !results.empty());
+    // If results are empty, we should return an error.
+    bool empty_list_on_ok = (error == OK && results.empty());
+    UMA_HISTOGRAM_BOOLEAN("DNS.EmptyAddressListAndNoError", empty_list_on_ok);
+    if (empty_list_on_ok)
+      error = ERR_NAME_NOT_RESOLVED;
 
     bool was_retry_attempt = attempt_number > 1;
 

net/dns/host_resolver_impl_unittest.cc

@@ -531,6 +531,17 @@ TEST_F(HostResolverImplTest, AsynchronousLookup) {
   EXPECT_EQ("just.testing", proc_->GetCaptureList()[0].hostname);
 }
 
+TEST_F(HostResolverImplTest, EmptyListMeansNameNotResolved) {
+  proc_->AddRuleForAllFamilies("just.testing", "");
+  proc_->SignalMultiple(1u);
+
+  Request* req = CreateRequest("just.testing", 80);
+  EXPECT_EQ(ERR_IO_PENDING, req->Resolve());
+  EXPECT_EQ(ERR_NAME_NOT_RESOLVED, req->WaitForResult());
+  EXPECT_EQ(0u, req->NumberOfAddresses());
+  EXPECT_EQ("just.testing", proc_->GetCaptureList()[0].hostname);
+}
+
 TEST_F(HostResolverImplTest, FailedAsynchronousLookup) {
   proc_->AddRuleForAllFamilies(std::string(),
                                "0.0.0.0");  // Default to failures.