2 files changed, 61 insertions, 4 deletions

diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index 2f2fa78d42..622a882a65 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -167,6 +167,9 @@ const nsIID kDEBUGWorkerEventTargetIID = {
 
 #endif
 
+// The number of nested timeouts before we start clamping. HTML says 5.
+const uint32_t kClampTimeoutNestingLevel = 5u;
+
 template <class T>
 class AutoPtrComparator
 {
@@ -1956,7 +1959,11 @@ NS_IMPL_QUERY_INTERFACE(WorkerLoadInfo::InterfaceRequestor, nsIInterfaceRequesto
 struct WorkerPrivate::TimeoutInfo
 {
   TimeoutInfo()
-  : mId(0), mIsInterval(false), mCanceled(false)
+  : mId(0)
+  , mNestingLevel(0)
+  , mIsInterval(false)
+  , mCanceled(false)
+  , mOnChromeWorker(false)
   {
     MOZ_COUNT_CTOR(mozilla::dom::workers::WorkerPrivate::TimeoutInfo);
   }
@@ -1976,12 +1983,33 @@ struct WorkerPrivate::TimeoutInfo
     return mTargetTime < aOther.mTargetTime;
   }
 
+  void AccumulateNestingLevel(const uint32_t& aBaseLevel) {
+    if (aBaseLevel < kClampTimeoutNestingLevel) {
+      mNestingLevel = aBaseLevel + 1;
+      return;
+    }
+    mNestingLevel = kClampTimeoutNestingLevel;
+  }
+
+  void CalculateTargetTime() {
+    auto target = mInterval;
+    // Clamp timeout for workers, except chrome workers
+    if (mNestingLevel >= kClampTimeoutNestingLevel && !mOnChromeWorker) {
+      target = TimeDuration::Max(
+          mInterval,
+          TimeDuration::FromMilliseconds(Preferences::GetInt("dom.min_timeout_value")));
+    }
+    mTargetTime = TimeStamp::Now() + target;
+  }
+
   nsCOMPtr<nsIScriptTimeoutHandler> mHandler;
   mozilla::TimeStamp mTargetTime;
   mozilla::TimeDuration mInterval;
   int32_t mId;
+  uint32_t mNestingLevel;
   bool mIsInterval;
   bool mCanceled;
+  bool mOnChromeWorker;
 };
 
 class WorkerJSContextStats final : public JS::RuntimeStats
@@ -4130,6 +4158,7 @@ WorkerPrivate::WorkerPrivate(WorkerPrivate* aParent,
   , mMainThreadEventTarget(do_GetMainThread())
   , mErrorHandlerRecursionCount(0)
   , mNextTimeoutId(1)
+  , mCurrentTimerNestingLevel(0)
   , mStatus(Pending)
   , mFrozen(false)
   , mTimerRunning(false)
@@ -6074,8 +6103,10 @@ WorkerPrivate::SetTimeout(JSContext* aCx,
   }
 
   nsAutoPtr<TimeoutInfo> newInfo(new TimeoutInfo());
+  newInfo->mOnChromeWorker = mIsChromeWorker;
   newInfo->mIsInterval = aIsInterval;
   newInfo->mId = timerId;
+  newInfo->AccumulateNestingLevel(this->mCurrentTimerNestingLevel);
 
   if (MOZ_UNLIKELY(timerId == INT32_MAX)) {
     NS_WARNING("Timeout ids overflowed!");
@@ -6188,14 +6219,21 @@ WorkerPrivate::RunExpiredTimeouts(JSContext* aCx)
   // Guard against recursion.
   mRunningExpiredTimeouts = true;
 
+  MOZ_DIAGNOSTIC_ASSERT(data->mCurrentTimerNestingLevel == 0);
+
   // Run expired timeouts.
   for (uint32_t index = 0; index < expiredTimeouts.Length(); index++) {
     TimeoutInfo*& info = expiredTimeouts[index];
+    AutoRestore<uint32_t> nestingLevel(this->mCurrentTimerNestingLevel);
 
     if (info->mCanceled) {
       continue;
     }
 
+    // Set current timer nesting level to current running timer handler's
+    // nesting level
+    this->mCurrentTimerNestingLevel = info->mNestingLevel;
+
     LOG(TimeoutsLog(), ("Worker %p executing timeout with original delay %f ms.\n",
                         this, info->mInterval.ToMilliseconds()));
 
@@ -6273,8 +6311,10 @@ WorkerPrivate::RunExpiredTimeouts(JSContext* aCx)
         info->mCanceled) {
       if (info->mIsInterval && !info->mCanceled) {
         // Reschedule intervals.
-        info->mTargetTime = info->mTargetTime + info->mInterval;
-        // Don't resort the list here, we'll do that at the end.
+        // Reschedule a timeout and, if needed, increase the nesting level.
+        info->AccumulateNestingLevel(info->mNestingLevel);
+        info->CalculateTargetTime();
+        // Don't re-sort the list here, we'll do that at the end.
         ++index;
       }
       else {
diff --git a/dom/workers/WorkerPrivate.h b/dom/workers/WorkerPrivate.h
index 351f5458f1..9effdccc9a 100644
--- a/dom/workers/WorkerPrivate.h
+++ b/dom/workers/WorkerPrivate.h
@@ -17,6 +17,7 @@
 
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/AutoRestore.h"
 #include "mozilla/CondVar.h"
 #include "mozilla/ConsoleReportCollector.h"
 #include "mozilla/DOMEventTargetHelper.h"
@@ -212,6 +213,9 @@ protected:
   RefPtr<EventTarget> mEventTarget;
   nsTArray<RefPtr<WorkerRunnable>> mPreStartRunnables;
 
+  // True if the worker is used in the UI
+  bool mIsChromeWorker;
+
 private:
   WorkerPrivate* mParent;
   nsString mScriptURL;
@@ -241,7 +245,6 @@ private:
   uint32_t mParentWindowPausedDepth;
   Status mParentStatus;
   bool mParentFrozen;
-  bool mIsChromeWorker;
   bool mMainThreadObjectsForgotten;
   // mIsSecureContext is set once in our constructor; after that it can be read
   // from various threads.  We could make this const if we were OK with setting
@@ -1016,6 +1019,20 @@ class WorkerPrivate : public WorkerPrivateParent<WorkerPrivate>
   uint32_t mErrorHandlerRecursionCount;
   uint32_t mNextTimeoutId;
   Status mStatus;
+
+  // Tracks the current setTimeout/setInterval nesting level.
+  // When there isn't a TimeoutHandler on the stack, this will be 0.
+  // Whenever setTimeout/setInterval are called, a new TimeoutInfo will be
+  // created with a nesting level one more than the current nesting level,
+  // saturating at the kClampTimeoutNestingLevel.
+  //
+  // When RunExpiredTimeouts is run, it sets this value to the
+  // TimeoutInfo::mNestingLevel for the duration of
+  // the WorkerScriptTimeoutHandler::Call which will explicitly trigger a
+  // microtask checkpoint so that any immediately-resolved promises will
+  // still see the nesting level.
+  uint32_t mCurrentTimerNestingLevel;
+
   bool mFrozen;
   bool mTimerRunning;
   bool mRunningExpiredTimeouts;