Perform scavenge in idle tasks.

src/heap/spaces.cc

Index: src/heap/spaces.cc
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 9bba6dd89b9cfe6e3e3ba0933d6d89b87dfc78ca..06618cdc726b0bde4cf153523e835756fc57f392 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -1415,11 +1415,9 @@ void NewSpace::UpdateInlineAllocationLimit(int size_in_bytes) {
     Address high = to_space_.page_high();
     Address new_top = allocation_info_.top() + size_in_bytes;
     allocation_info_.set_limit(Min(new_top, high));
-  } else if (inline_allocation_limit_step() == 0) {
-    // Normal limit is the end of the current page.
-    allocation_info_.set_limit(to_space_.page_high());
   } else {
     // Lower limit during incremental marking.
+    DCHECK(inline_allocation_limit_step_ != 0);
     Address high = to_space_.page_high();
     Address new_top = allocation_info_.top() + size_in_bytes;
     Address new_limit = new_top + inline_allocation_limit_step_;
@@ -1502,11 +1500,13 @@ bool NewSpace::EnsureAllocation(int size_in_bytes,
 
   if (allocation_info_.limit() < high) {
     // Either the limit has been lowered because linear allocation was disabled
-    // or because incremental marking wants to get a chance to do a step. Set
-    // the new limit accordingly.
+    // or because incremental marking wants to get a chance to do a step,
+    // or because idle scavenge job wants to get a chance to post a task.
+    // Set the new limit accordingly.
     if (top_on_previous_step_) {
       Address new_top = old_top + aligned_size_in_bytes;
       int bytes_allocated = static_cast<int>(new_top - top_on_previous_step_);
+      heap()->ScheduleIdleScavengeIfNeeded(bytes_allocated);
       heap()->incremental_marking()->Step(
           bytes_allocated, IncrementalMarking::GC_VIA_STACK_GUARD);
       top_on_previous_step_ = new_top;