Bug 1470260 - Part 2: Make RefreshDriverTimer ref-counted and hold a strong ref on it on the stack when nsRefreshDriver::Tick can be reached.

1 files changed, 21 insertions, 20 deletions

diff --git a/layout/base/nsRefreshDriver.cpp b/layout/base/nsRefreshDriver.cpp
index 8a62b517e..b975a69dd 100644
--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -143,11 +143,7 @@ public:
   {
   }
 
-  virtual ~RefreshDriverTimer()
-  {
-    MOZ_ASSERT(mContentRefreshDrivers.Length() == 0, "Should have removed all content refresh drivers from here by now!");
-    MOZ_ASSERT(mRootRefreshDrivers.Length() == 0, "Should have removed all root refresh drivers from here by now!");
-  }
+  NS_INLINE_DECL_REFCOUNTING(RefreshDriverTimer)
 
   virtual void AddRefreshDriver(nsRefreshDriver* aDriver)
   {
@@ -253,6 +249,12 @@ public:
   }
 
 protected:
+  virtual ~RefreshDriverTimer()
+  {
+    MOZ_ASSERT(mContentRefreshDrivers.Length() == 0, "Should have removed all content refresh drivers from here by now!");
+    MOZ_ASSERT(mRootRefreshDrivers.Length() == 0, "Should have removed all root refresh drivers from here by now!");
+  }
+
   virtual void StartTimer() = 0;
   virtual void StopTimer() = 0;
   virtual void ScheduleNextTick(TimeStamp aNowTime) = 0;
@@ -335,10 +337,11 @@ protected:
   nsTArray<RefPtr<nsRefreshDriver> > mRootRefreshDrivers;
 
   // useful callback for nsITimer-based derived classes, here
-  // bacause of c++ protected shenanigans
+  // because of c++ protected shenanigans
   static void TimerTick(nsITimer* aTimer, void* aClosure)
   {
-    RefreshDriverTimer *timer = static_cast<RefreshDriverTimer*>(aClosure);
+    RefPtr<RefreshDriverTimer> timer = 
+      static_cast<RefreshDriverTimer*>(aClosure);
     timer->Tick();
   }
 };
@@ -459,9 +462,7 @@ public:
 private:
   // Since VsyncObservers are refCounted, but the RefreshDriverTimer are
   // explicitly shutdown. We create an inner class that has the VsyncObserver
-  // and is shutdown when the RefreshDriverTimer is deleted. The alternative is
-  // to (a) make all RefreshDriverTimer RefCounted or (b) use different
-  // VsyncObserver types.
+  // and is shutdown when the RefreshDriverTimer is deleted.
   class RefreshDriverVsyncObserver final : public VsyncObserver
   {
   public:
@@ -576,7 +577,9 @@ private:
       // the scheduled TickRefreshDriver() runs. Check mVsyncRefreshDriverTimer
       // before use.
       if (mVsyncRefreshDriverTimer) {
-        mVsyncRefreshDriverTimer->RunRefreshDrivers(aVsyncTimestamp);
+        RefPtr<VsyncRefreshDriverTimer> timer = mVsyncRefreshDriverTimer;
+        timer->RunRefreshDrivers(aVsyncTimestamp);
+        // Note: mVsyncRefreshDriverTimer might be null now.
       }
     }
 
@@ -829,7 +832,8 @@ protected:
 
   static void TimerTickOne(nsITimer* aTimer, void* aClosure)
   {
-    InactiveRefreshDriverTimer *timer = static_cast<InactiveRefreshDriverTimer*>(aClosure);
+    RefPtr<InactiveRefreshDriverTimer> timer = 
+      static_cast<InactiveRefreshDriverTimer*>(aClosure);
     timer->TickOne();
   }
 
@@ -881,8 +885,8 @@ NS_IMPL_ISUPPORTS(VsyncChildCreateCallback, nsIIPCBackgroundChildCreateCallback)
 
 } // namespace mozilla
 
-static RefreshDriverTimer* sRegularRateTimer;
-static InactiveRefreshDriverTimer* sThrottledRateTimer;
+static StaticRefPtr<RefreshDriverTimer> sRegularRateTimer;
+static StaticRefPtr<InactiveRefreshDriverTimer> sThrottledRateTimer;
 
 #ifdef XP_WIN
 static int32_t sHighPrecisionTimerRequests = 0;
@@ -964,8 +968,6 @@ GetFirstFrameDelay(imgIRequest* req)
 nsRefreshDriver::Shutdown()
 {
   // clean up our timers
-  delete sRegularRateTimer;
-  delete sThrottledRateTimer;
 
   sRegularRateTimer = nullptr;
   sThrottledRateTimer = nullptr;
@@ -2229,16 +2231,15 @@ nsRefreshDriver::PVsyncActorCreated(VsyncChild* aVsyncChild)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(!XRE_IsParentProcess());
-  auto* vsyncRefreshDriverTimer =
-      new VsyncRefreshDriverTimer(aVsyncChild);
+  RefPtr<RefreshDriverTimer> vsyncRefreshDriverTimer =
+    new VsyncRefreshDriverTimer(aVsyncChild);
 
   // If we are using software timer, swap current timer to
   // VsyncRefreshDriverTimer.
   if (sRegularRateTimer) {
     sRegularRateTimer->SwapRefreshDrivers(vsyncRefreshDriverTimer);
-    delete sRegularRateTimer;
   }
-  sRegularRateTimer = vsyncRefreshDriverTimer;
+  sRegularRateTimer = vsyncRefreshDriverTimer.forget();
 }
 
 void