Fix PepperGamepadHostTest.WaitForReply

content/browser/gamepad/gamepad_service.cc

Index: content/browser/gamepad/gamepad_service.cc
diff --git a/content/browser/gamepad/gamepad_service.cc b/content/browser/gamepad/gamepad_service.cc
index 42b1e10821607d112203d281e86698894d2a0f01..67930f6118d16de2468d3d3968b68fb5abbec077 100644
--- a/content/browser/gamepad/gamepad_service.cc
+++ b/content/browser/gamepad/gamepad_service.cc
@@ -22,23 +22,27 @@ GamepadService* g_gamepad_service = 0;
 GamepadService::GamepadService()
     : num_active_consumers_(0),
       gesture_callback_pending_(false) {
-  SetInstance();
+  SetInstance(this);
 }
 
 GamepadService::GamepadService(scoped_ptr<GamepadDataFetcher> fetcher)
     : provider_(new GamepadProvider(fetcher.Pass())),
       num_active_consumers_(0),
       gesture_callback_pending_(false) {
-  SetInstance();
+  SetInstance(this);
   thread_checker_.DetachFromThread();
 }
 
 GamepadService::~GamepadService() {
+  SetInstance(NULL);
 }
 
-void GamepadService::SetInstance() {
-  CHECK(!g_gamepad_service);
-  g_gamepad_service = this;
+void GamepadService::SetInstance(GamepadService* instance) {
+  // Unit tests can create multiple instances but only one should exist at any
+  // given time so g_gamepad_service should only go from NULL to non-NULL and
+  // vica versa.
+  CHECK(!!instance != !!g_gamepad_service);
+  g_gamepad_service = instance;
 }
 
 GamepadService* GamepadService::GetInstance() {