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

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

Index: third_party/WebKit/Source/platform/heap/ThreadState.cpp
diff --git a/third_party/WebKit/Source/platform/heap/ThreadState.cpp b/third_party/WebKit/Source/platform/heap/ThreadState.cpp
index 53497e71765aa20f04d9c4cb0688c20de2592bc1..2627bc0dee768a66fdfb450e14ef396ffadc59fd 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadState.cpp
+++ b/third_party/WebKit/Source/platform/heap/ThreadState.cpp
@@ -334,7 +334,10 @@ void ThreadState::cleanupMainThread() {
 #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
 
@@ -1500,6 +1503,18 @@ void ThreadState::registerStaticPersistentNode(
   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;