Release Oilpan heap singletons prior to LSan leak detection.

third_party/WebKit/Source/web/WebKit.cpp

Index: third_party/WebKit/Source/web/WebKit.cpp
diff --git a/third_party/WebKit/Source/web/WebKit.cpp b/third_party/WebKit/Source/web/WebKit.cpp
index c892d8b06b2c170be6d89a38a70f71033ec2914e..f6375b0ad367a324edcdb4297a9d97207a419b5e 100644
--- a/third_party/WebKit/Source/web/WebKit.cpp
+++ b/third_party/WebKit/Source/web/WebKit.cpp
@@ -195,6 +195,21 @@ void initializeWithoutV8(Platform* platform)
 
 void shutdown()
 {
+#if defined(LEAK_SANITIZER)
+    // If LSan is about to perform leak detection, release all the registered
+    // static Persistent<> root references to global caches that Blink keeps,
+    // followed by GCs to clear out all they referred to. A full v8 GC cycle
+    // is needed to flush out all garbage.
+    //
+    // This is not needed for caches over non-Oilpan objects, as they're
+    // not scanned by LSan due to being held in non-global storage
+    // ("static" references inside functions/methods.)
+    if (ThreadState* threadState = ThreadState::current()) {
+        threadState->releaseStaticPersistentNodes();
+        Heap::collectAllGarbage();
+    }
+#endif
+
     // currentThread() is null if we are running on a thread without a message loop.
     if (Platform::current()->currentThread()) {
         Platform::current()->unregisterMemoryDumpProvider(WebCacheMemoryDumpProvider::instance());