cros: Do not schedule attempt when behind captive portal with response 200 is detected

Changes:
(1) Do not schedule attempt if we are already behind captive portal with response 200, which can be either the result of NetworkPortalDetector or shill's detection. In test, this can reduce the call times of CaptivePortalDetector::DetectCaptivePortal from 6+ to 2~3 within 10s.
(2) modify tests to adapt this change

BUG=702273
TEST=If we log in CaptivePortalDetector::DetectCaptivePortal, we can see the attempts reduced to 2~3 for connecting to captive portal wifi.

Review-Url: https://codereview.chromium.org/2756643002
Cr-Commit-Position: refs/heads/master@{#457829}

chrome/browser/chromeos/net/network_portal_detector_impl.cc

@@ -551,8 +551,15 @@ void NetworkPortalDetectorImpl::OnAttemptCompleted(
   }
 
   // Observers (via OnDetectionCompleted) may already schedule new attempt.
-  if (is_idle())
-    ScheduleAttempt(results.retry_after_delta);
+  if (!is_idle())
+    return;
+
+  // If behind a captive portal and the response code was 200 (OK), do not
+  // schedule a new attempt.
+  if (state.status == CAPTIVE_PORTAL_STATUS_PORTAL && response_code == 200)
+    return;
+
+  ScheduleAttempt(results.retry_after_delta);
 }
 
 void NetworkPortalDetectorImpl::Observe(

chrome/browser/chromeos/net/network_portal_detector_impl_unittest.cc

@@ -334,7 +334,7 @@ TEST_F(NetworkPortalDetectorImplTest, Portal) {
 
   CompleteURLFetch(net::OK, 200, nullptr);
 
-  ASSERT_FALSE(is_state_idle());
+  ASSERT_TRUE(is_state_idle());
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
 
@@ -425,7 +425,7 @@ TEST_F(NetworkPortalDetectorImplTest, TwoNetworks) {
 
   // WiFi is in portal state.
   CompleteURLFetch(net::OK, 200, nullptr);
-  ASSERT_FALSE(is_state_idle());
+  ASSERT_TRUE(is_state_idle());
 
   SetConnected(kStubEthernet);
   ASSERT_TRUE(is_state_checking_for_portal());
@@ -508,7 +508,7 @@ TEST_F(NetworkPortalDetectorImplTest, NetworkStateChanged) {
 
   CompleteURLFetch(net::OK, 200, nullptr);
 
-  ASSERT_FALSE(is_state_idle());
+  ASSERT_TRUE(is_state_idle());
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
 
@@ -526,7 +526,7 @@ TEST_F(NetworkPortalDetectorImplTest, NetworkStateChanged) {
 
   CompleteURLFetch(net::OK, 200, nullptr);
 
-  ASSERT_FALSE(is_state_idle());
+  ASSERT_TRUE(is_state_idle());
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
 
@@ -825,7 +825,7 @@ TEST_F(NetworkPortalDetectorImplTest, ErrorScreenStrategyForPortalNetwork) {
 
   CompleteURLFetch(net::OK, 200, nullptr);
   ASSERT_EQ(0, no_response_result_count());
-  ASSERT_TRUE(is_state_portal_detection_pending());
+  ASSERT_TRUE(is_state_idle());
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
 
@@ -834,6 +834,7 @@ TEST_F(NetworkPortalDetectorImplTest, ErrorScreenStrategyForPortalNetwork) {
 
   disable_error_screen_strategy();
 
+  // Set a different strategy will Start detection if idle.
   ASSERT_TRUE(is_state_portal_detection_pending());
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
@@ -887,7 +888,7 @@ TEST_F(NetworkPortalDetectorImplTest, TestDetectionRestart) {
 
   CheckPortalState(
       NetworkPortalDetector::CAPTIVE_PORTAL_STATUS_PORTAL, 200, kStubWireless1);
-  ASSERT_FALSE(is_state_idle());
+  ASSERT_TRUE(is_state_idle());
 
   ASSERT_TRUE(
       MakeResultHistogramChecker()