[Geolocation] Fix a race condition in GeolocationArbitratorImpl

Previously, the following sequence of events was possible:
  (1) StartProviders() posts an asynchronous task T to continue startup.
  (2) StopProviders() is called.
  (3) T comes back, and startup continues.

Now, step (3) will short-circuit so that startup does not continue if the
asynchronous continuation comes in after StopProviders() is called.

BUG=166596

Review URL: https://chromiumcodereview.appspot.com/14864017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@200399 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 8 insertions, 2 deletions

diff --git a/content/browser/geolocation/location_arbitrator_impl.cc b/content/browser/geolocation/location_arbitrator_impl.cc
index 7720c55..4fa19b5 100644
--- a/content/browser/geolocation/location_arbitrator_impl.cc
+++ b/content/browser/geolocation/location_arbitrator_impl.cc
@@ -29,7 +29,8 @@ GeolocationArbitratorImpl::GeolocationArbitratorImpl(
     const LocationUpdateCallback& callback)
     : callback_(callback),
       position_provider_(NULL),
-      is_permission_granted_(false) {
+      is_permission_granted_(false),
+      is_running_(false) {
 }
 
 GeolocationArbitratorImpl::~GeolocationArbitratorImpl() {
@@ -49,6 +50,7 @@ void GeolocationArbitratorImpl::OnPermissionGranted() {
 
 void GeolocationArbitratorImpl::StartProviders(bool use_high_accuracy) {
   // Stash options as OnAccessTokenStoresLoaded has not yet been called.
+  is_running_ = true;
   use_high_accuracy_ = use_high_accuracy;
   if (providers_.empty()) {
     DCHECK(DefaultNetworkProviderURL().is_valid());
@@ -69,12 +71,13 @@ void GeolocationArbitratorImpl::DoStartProviders() {
 
 void GeolocationArbitratorImpl::StopProviders() {
   providers_.clear();
+  is_running_ = false;
 }
 
 void GeolocationArbitratorImpl::OnAccessTokenStoresLoaded(
     AccessTokenStore::AccessTokenSet access_token_set,
     net::URLRequestContextGetter* context_getter) {
-  if (!providers_.empty()) {
+  if (!is_running_ || !providers_.empty()) {
     // A second StartProviders() call may have arrived before the first
     // completed.
     return;
diff --git a/content/browser/geolocation/location_arbitrator_impl.h b/content/browser/geolocation/location_arbitrator_impl.h
index 38265af..f4eb4e9 100644
--- a/content/browser/geolocation/location_arbitrator_impl.h
+++ b/content/browser/geolocation/location_arbitrator_impl.h
@@ -92,6 +92,9 @@ class CONTENT_EXPORT GeolocationArbitratorImpl
   // The current best estimate of our position.
   Geoposition position_;
 
+  // Tracks whether providers should be running.
+  bool is_running_;
+
   DISALLOW_COPY_AND_ASSIGN(GeolocationArbitratorImpl);
 };