Fix GCMClient delayed then immediate start.

Commit 9f9a73672ab60c3da17bd4ff2660ce3a113cd8fa
(https://codereview.chromium.org/1183843002) has a race condition, where
calling GCMClient::Start(DELAYED_START) closely followed by
GCMClient::Start(IMMEDIATE_START) fails to create the GCM store.

This patch fixes that case.

BUG=522902

Review URL: https://codereview.chromium.org/1310563003

Cr-Commit-Position: refs/heads/master@{#344875}

2 files changed, 25 insertions, 4 deletions

diff --git a/components/gcm_driver/gcm_client_impl.cc b/components/gcm_driver/gcm_client_impl.cc
index 6db36cb..1a95809 100644
--- a/components/gcm_driver/gcm_client_impl.cc
+++ b/components/gcm_driver/gcm_client_impl.cc
@@ -381,10 +381,18 @@ void GCMClientImpl::OnLoadCompleted(scoped_ptr<GCMStore::LoadResult> result) {
 
   if (!result->success) {
     if (result->store_does_not_exist) {
-      // In the case that the store does not exist, set |state| back to
-      // INITIALIZED such that store loading could be triggered again when
-      // Start() is called with IMMEDIATE_START.
-      state_ = INITIALIZED;
+      if (start_mode_ == IMMEDIATE_START) {
+        // An immediate start was requested during the delayed start that just
+        // completed. Perform it now.
+        gcm_store_->Load(GCMStore::CREATE_IF_MISSING,
+                         base::Bind(&GCMClientImpl::OnLoadCompleted,
+                                    weak_ptr_factory_.GetWeakPtr()));
+      } else {
+        // In the case that the store does not exist, set |state_| back to
+        // INITIALIZED such that store loading could be triggered again when
+        // Start() is called with IMMEDIATE_START.
+        state_ = INITIALIZED;
+      }
     } else {
       // Otherwise, destroy the store to try again.
       ResetStore();
diff --git a/components/gcm_driver/gcm_client_impl_unittest.cc b/components/gcm_driver/gcm_client_impl_unittest.cc
index 876e2f9..3fbb2e7 100644
--- a/components/gcm_driver/gcm_client_impl_unittest.cc
+++ b/components/gcm_driver/gcm_client_impl_unittest.cc
@@ -1307,6 +1307,19 @@ TEST_F(GCMClientImplStartAndStopTest, ImmediateStartAndThenDelayStart) {
   EXPECT_EQ(GCMClientImpl::LOADED, gcm_client_state());
 }
 
+TEST_F(GCMClientImplStartAndStopTest, DelayedStartRace) {
+  // GCMClientImpl should be in INITIALIZED state at first.
+  EXPECT_EQ(GCMClientImpl::INITIALIZED, gcm_client_state());
+
+  // Delay start the GCM, then start it immediately while it's still loading.
+  gcm_client()->Start(GCMClient::DELAYED_START);
+  gcm_client()->Start(GCMClient::IMMEDIATE_START);
+  PumpLoopUntilIdle();
+  EXPECT_EQ(GCMClientImpl::INITIAL_DEVICE_CHECKIN, gcm_client_state());
+  DefaultCompleteCheckin();
+  EXPECT_EQ(GCMClientImpl::READY, gcm_client_state());
+}
+
 TEST_F(GCMClientImplStartAndStopTest, DelayedStart) {
   // GCMClientImpl should be in INITIALIZED state at first.
   EXPECT_EQ(GCMClientImpl::INITIALIZED, gcm_client_state());