sync: Fix bug in early sync shutdown

In r224014, we tried to fix many issues with early shutdown.  That CL
contained a fairly serious bug that would cause shutdown requests that
arrive very early to trigger a crash.

This patch fixes that bug and adds a test to help prevent regressions.

BUG=236451,303177

Review URL: https://codereview.chromium.org/25794002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226793 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 32 insertions, 3 deletions

diff --git a/sync/internal_api/http_bridge.cc b/sync/internal_api/http_bridge.cc
index 48305eb..5827c9d 100644
--- a/sync/internal_api/http_bridge.cc
+++ b/sync/internal_api/http_bridge.cc
@@ -79,9 +79,9 @@ void HttpBridgeFactory::Init(const std::string& user_agent) {
   base::AutoLock lock(context_getter_lock_);
 
   if (!baseline_request_context_getter_.get()) {
-    // Uh oh.  We've been aborted before we finsihed initializing.
-    // There's no point in initializating further; let's just return
-    // right away.
+    // Uh oh.  We've been aborted before we finished initializing.  There's no
+    // point in initializating further; let's just return right away.
+    return;
   }
 
   request_context_getter_ =
diff --git a/sync/internal_api/http_bridge_unittest.cc b/sync/internal_api/http_bridge_unittest.cc
index e1dc6de..5dd39bb 100644
--- a/sync/internal_api/http_bridge_unittest.cc
+++ b/sync/internal_api/http_bridge_unittest.cc
@@ -488,4 +488,33 @@ TEST_F(SyncHttpBridgeTest, RequestContextGetterReleaseOrder) {
   sync_thread.Stop();
 }
 
+// Attempt to release the URLRequestContextGetter before the HttpBridgeFactory
+// is initialized.
+TEST_F(SyncHttpBridgeTest, EarlyAbortFactory) {
+  // In a real scenario, the following would happen on many threads.  For
+  // simplicity, this test uses only one thread.
+
+  scoped_refptr<net::URLRequestContextGetter> baseline_context_getter(
+      new net::TestURLRequestContextGetter(io_thread()->message_loop_proxy()));
+  CancelationSignal release_request_context_signal;
+
+  // UI Thread: Initialize the HttpBridgeFactory.  The next step would be to
+  // post a task to SBH::Core to have it initialized.
+  scoped_ptr<syncer::HttpBridgeFactory> factory(new HttpBridgeFactory(
+      baseline_context_getter,
+      NetworkTimeUpdateCallback(),
+      &release_request_context_signal));
+
+  // UI Thread: A very early shutdown request arrives and executes on the UI
+  // thread before the posted sync thread task is run.
+  release_request_context_signal.Signal();
+
+  // Sync thread: Finally run the posted task, only to find that our
+  // HttpBridgeFactory has been neutered.  Should not crash.
+  factory->Init("TestUserAgent");
+
+  // At this point, attempting to use the factory would trigger a crash.  Both
+  // this test and the real world code should make sure this never happens.
+};
+
 }  // namespace syncer