Add some temporary CHECKs to verify theories about infinite loops/hangs

Bug: 1021630
Change-Id: I50f835362b404f7c5e8828d70581078b7145f322
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1937067
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719544}

third_party/blink/renderer/core/svg/animation/smil_time_container.cc

@@ -454,6 +454,9 @@ void SMILTimeContainer::UpdateIntervals(SMILTime document_time) {
   DCHECK_GE(document_time, SMILTime());
   DCHECK(!priority_queue_.IsEmpty());
 
+  const size_t kMaxIterations = std::max(priority_queue_.size() * 16, 1000000u);
+  size_t current_iteration = 0;
+
   base::AutoReset<bool> updating_intervals_scope(&is_updating_intervals_, true);
   while (priority_queue_.Min() <= document_time) {
     SVGSMILElement* element = priority_queue_.MinElement();
@@ -462,6 +465,8 @@ void SMILTimeContainer::UpdateIntervals(SMILTime document_time) {
     SMILTime next_interval_time =
         element->ComputeNextIntervalTime(document_time);
     priority_queue_.Update(next_interval_time, element);
+    // Debugging signal for crbug.com/1021630.
+    CHECK_LT(current_iteration++, kMaxIterations);
   }
 }
 

third_party/blink/renderer/core/svg/animation/svg_smil_element.cc

@@ -772,6 +772,8 @@ SMILInterval SVGSMILElement::ResolveInterval(SMILTime begin_after,
                                              SMILTime end_after) const {
   // Simplified version of the pseudocode in
   // http://www.w3.org/TR/SMIL3/smil-timing.html#q90.
+  const size_t kMaxIterations = std::max(begin_times_.size() * 4, 1000000u);
+  size_t current_iteration = 0;
   while (true) {
     SMILTime temp_begin = FindInstanceTime(kBegin, begin_after, true);
     if (temp_begin.IsUnresolved())
@@ -788,6 +790,8 @@ SMILInterval SVGSMILElement::ResolveInterval(SMILTime begin_after,
     if (begin_after == temp_end)
       temp_end = begin_after + SMILTime::Epsilon();
     begin_after = temp_end;
+    // Debugging signal for crbug.com/1021630.
+    CHECK_LT(current_iteration++, kMaxIterations);
   }
   return SMILInterval::Unresolved();
 }