Lend LSan a hand and clear out singleton static persistents first.

third_party/WebKit/Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 316 matching lines @@
   // point on will not trace objects on this thread's arenas.
   cleanupPages();
 }
 
 void ThreadState::cleanupMainThread() {
   ASSERT(isMainThread());
 
 #if defined(LEAK_SANITIZER)
   // See comment below, clear out most garbage before releasing static
   // persistents should some of the finalizers depend on touching
-  // these persistents.
+  // these persistents. The clearing done includes the static persistents,
+  // so as to make objects retained by these singletons also be eligible
+  // for garbage collection right away.
+  clearStaticPersistentNodes();

[haraken, 2017/01/02 09:26:44]

Hmm, I'm not quite sure if this helps.

In my understanding, LSan on a renderer process runs before blink::shutdown
getting called. See
https://cs.chromium.org/chromium/src/content/renderer/renderer_main.cc?sq=pac...

__lsan_do_leak_check() is called before RenderProcessImpl's object gets
destructed, in which blink::shutdown is called.

[sof, 2017/01/02 09:37:16]

Hmm, that doesn't make a lot of sense, given the trouble that LSan has given us
in the past by not clearing up and GCing first.

   collectAllGarbage();
 #endif
 
   releaseStaticPersistentNodes();
 
 #if defined(LEAK_SANITIZER)
   // If LSan is about to perform leak detection, after having released all
   // the registered static Persistent<> root references to global caches
   // that Blink keeps, follow up with a round of GCs to clear out all
   // what they referred to.
@@ skipping 1145 matching lines @@
     PersistentClearCallback callback) {
 #if defined(LEAK_SANITIZER)
   if (m_disabledStaticPersistentsRegistration)
     return;
 #endif
 
   ASSERT(!m_staticPersistents.contains(node));
   m_staticPersistents.add(node, callback);
 }
 
+#if defined(LEAK_SANITIZER)
+void ThreadState::clearStaticPersistentNodes() {
+  HashMap<PersistentNode*, ThreadState::PersistentClearCallback>
+      staticPersistents;
+  staticPersistents.swap(m_staticPersistents);
+
+  PersistentRegion* persistentRegion = getPersistentRegion();
+  for (const auto& it : staticPersistents)
+    persistentRegion->clearPersistentNode(it.key, it.value);
+}
+#endif
+
 void ThreadState::releaseStaticPersistentNodes() {
   HashMap<PersistentNode*, ThreadState::PersistentClearCallback>
       staticPersistents;
   staticPersistents.swap(m_staticPersistents);
 
   PersistentRegion* persistentRegion = getPersistentRegion();
   for (const auto& it : staticPersistents)
     persistentRegion->releasePersistentNode(it.key, it.value);
 }
 
@@ skipping 364 matching lines @@
     collectGarbage(BlinkGC::NoHeapPointersOnStack, BlinkGC::GCWithSweep,
                    BlinkGC::ForcedGC);
     size_t liveObjects = heap().heapStats().markedObjectSize();
     if (liveObjects == previousLiveObjects)
       break;
     previousLiveObjects = liveObjects;
   }
 }
 
 }  // namespace blink