From b024b00b94818ffe701570c97804711fe77fceac Mon Sep 17 00:00:00 2001
From: Olli Pettay <Olli.Pettay@helsinki.fi>
Date: Mon, 15 Apr 2019 15:41:15 +0000
Subject: [PATCH] Bug 1515216, ensure IdleTaskRunners are added only once to
 RefreshDriver's idle runnable list, r=mccr8

Differential Revision: https://phabricator.services.mozilla.com/D27424

--HG--
extra : moz-landing-system : lando
---
 layout/base/nsRefreshDriver.cpp  | 10 ++++++++--
 layout/base/nsRefreshDriver.h    |  4 ++--
 xpcom/threads/IdleTaskRunner.cpp |  2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/layout/base/nsRefreshDriver.cpp b/layout/base/nsRefreshDriver.cpp
index 0037cf3bcb76..46c951e4a118 100644
--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -1713,10 +1713,16 @@ struct RunnableWithDelay {
 
 static AutoTArray<RunnableWithDelay, 8>* sPendingIdleRunnables = nullptr;
 
-void nsRefreshDriver::DispatchIdleRunnableAfterTick(nsIRunnable* aRunnable,
-                                                    uint32_t aDelay) {
+void nsRefreshDriver::DispatchIdleRunnableAfterTickUnlessExists(
+    nsIRunnable* aRunnable, uint32_t aDelay) {
   if (!sPendingIdleRunnables) {
     sPendingIdleRunnables = new AutoTArray<RunnableWithDelay, 8>();
+  } else {
+    for (uint32_t i = 0; i < sPendingIdleRunnables->Length(); ++i) {
+      if ((*sPendingIdleRunnables)[i].mRunnable == aRunnable) {
+        return;
+      }
+    }
   }
 
   RunnableWithDelay rwd = {aRunnable, aDelay};
diff --git a/layout/base/nsRefreshDriver.h b/layout/base/nsRefreshDriver.h
index 0e73047a536d..8763be8ceff1 100644
--- a/layout/base/nsRefreshDriver.h
+++ b/layout/base/nsRefreshDriver.h
@@ -415,8 +415,8 @@ class nsRefreshDriver final : public mozilla::layers::TransactionIdAllocator,
    */
   static mozilla::Maybe<mozilla::TimeStamp> GetNextTickHint();
 
-  static void DispatchIdleRunnableAfterTick(nsIRunnable* aRunnable,
-                                            uint32_t aDelay);
+  static void DispatchIdleRunnableAfterTickUnlessExists(nsIRunnable* aRunnable,
+                                                        uint32_t aDelay);
   static void CancelIdleRunnable(nsIRunnable* aRunnable);
 
   void NotifyDOMContentLoaded();
diff --git a/xpcom/threads/IdleTaskRunner.cpp b/xpcom/threads/IdleTaskRunner.cpp
index d76fa24d78c5..038efad6617a 100644
--- a/xpcom/threads/IdleTaskRunner.cpp
+++ b/xpcom/threads/IdleTaskRunner.cpp
@@ -119,7 +119,7 @@ void IdleTaskRunner::Schedule(bool aAllowIdleDispatch) {
   TimeStamp hint = nsRefreshDriver::GetIdleDeadlineHint(now);
   if (hint != now) {
     // RefreshDriver is ticking, let it schedule the idle dispatch.
-    nsRefreshDriver::DispatchIdleRunnableAfterTick(this, mDelay);
+    nsRefreshDriver::DispatchIdleRunnableAfterTickUnlessExists(this, mDelay);
     // Ensure we get called at some point, even if RefreshDriver is stopped.
     SetTimerInternal(mDelay);
   } else {