Fix PepperGamepadHostTest.WaitForReply

Fixup after "Gamepad: don't notify about connected pads twice".
The CHECK(!g_gamepad_service) I added is failing because during
unit tests several instance can be created and destroyed.

R=bajones@chromium.org
BUG=391503

Review URL: https://codereview.chromium.org/372053004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281959 0039d316-1c4b-4281-b951-d872f2087c98

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() {

content/browser/gamepad/gamepad_service.h

@@ -92,7 +92,7 @@ class CONTENT_EXPORT GamepadService {
 
   virtual ~GamepadService();
 
-  void SetInstance();
+  static void SetInstance(GamepadService*);
 
   void OnUserGesture();
 

tools/valgrind/gtest_exclude/content_unittests.gtest.txt

@@ -5,6 +5,3 @@ CompositingIOSurfaceTransformerTest.*
 # False positive, according to crbug.com/386080
 WebLayerImplFixedBoundsTest.CompareToWebLayerImplComplex
 WebLayerImplFixedBoundsTest.CompareToWebLayerImplSimple
-
-# crbug.com/391503
-PepperGamepadHostTest.WaitForReply