[heap] Pass external memory callback flags on external memory pressure.

This patch ensures that all code path of the external memory pressure
handler pass the kGCCallbackFlagCollectAllExternalMemory flag to the
embedder. This is necessary to force Oilpan GC.

Bug: chromium:733655
Change-Id: I2e680d1e7f9087d1930d56ead39ef7cf1bc93e56
Reviewed-on: https://chromium-review.googlesource.com/616149Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47378}

src/heap/heap.cc

@@ -1069,26 +1069,28 @@ void Heap::CollectAllAvailableGarbage(GarbageCollectionReason gc_reason) {
 }
 
 void Heap::ReportExternalMemoryPressure() {
+  const GCCallbackFlags kGCCallbackFlagsForExternalMemory =
+      static_cast<GCCallbackFlags>(
+          kGCCallbackFlagSynchronousPhantomCallbackProcessing |
+          kGCCallbackFlagCollectAllExternalMemory);
   if (external_memory_ >
       (external_memory_at_last_mark_compact_ + external_memory_hard_limit())) {
     CollectAllGarbage(
         kReduceMemoryFootprintMask | kFinalizeIncrementalMarkingMask,
         GarbageCollectionReason::kExternalMemoryPressure,
         static_cast<GCCallbackFlags>(kGCCallbackFlagCollectAllAvailableGarbage |
-                                     kGCCallbackFlagCollectAllExternalMemory));
+                                     kGCCallbackFlagsForExternalMemory));
     return;
   }
   if (incremental_marking()->IsStopped()) {
     if (incremental_marking()->CanBeActivated()) {
-      StartIncrementalMarking(
-          i::Heap::kNoGCFlags, GarbageCollectionReason::kExternalMemoryPressure,
-          static_cast<GCCallbackFlags>(
-              kGCCallbackFlagSynchronousPhantomCallbackProcessing |
-              kGCCallbackFlagCollectAllExternalMemory));
+      StartIncrementalMarking(i::Heap::kNoGCFlags,
+                              GarbageCollectionReason::kExternalMemoryPressure,
+                              kGCCallbackFlagsForExternalMemory);
     } else {
       CollectAllGarbage(i::Heap::kNoGCFlags,
                         GarbageCollectionReason::kExternalMemoryPressure,
-                        kGCCallbackFlagSynchronousPhantomCallbackProcessing);
+                        kGCCallbackFlagsForExternalMemory);
     }
   } else {
     // Incremental marking is turned on an has already been started.
@@ -1099,6 +1101,9 @@ void Heap::ReportExternalMemoryPressure() {
             Max(kMinStepSize, static_cast<double>(external_memory_) /
                                   external_memory_limit_ * kMinStepSize));
     const double deadline = MonotonicallyIncreasingTimeInMs() + ms_step;
+    // Extend the gc callback flags with external memory flags.
+    current_gc_callback_flags_ = static_cast<GCCallbackFlags>(
+        current_gc_callback_flags_ | kGCCallbackFlagsForExternalMemory);
     incremental_marking()->AdvanceIncrementalMarking(
         deadline, IncrementalMarking::GC_VIA_STACK_GUARD,
         IncrementalMarking::FORCE_COMPLETION, StepOrigin::kV8);