LeakDetector should run a GC on the compositor thread

Compositor workers do not own the compositor thread so they do not do a cleanup gc on termination. This means objects will be left uncollected once per thread heap is enabled for compositor workers. To make up for that, the LeakDetector should run a GC on the compositor thread explicitly.

BUG=

Review-Url: https://codereview.chromium.org/2304073002
Cr-Commit-Position: refs/heads/master@{#417574}

third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.cpp

@@ -24,10 +24,10 @@ namespace {
 // case.
 class BackingThreadHolder {
 public:
-    static BackingThreadHolder& instance()
+    static BackingThreadHolder* instance()
     {
         MutexLocker locker(holderInstanceMutex());
-        return *s_instance;
+        return s_instance;
     }
 
     static void ensureInstance()
@@ -112,7 +112,24 @@ AbstractAnimationWorkletThread::~AbstractAnimationWorkletThread()
 
 WorkerBackingThread& AbstractAnimationWorkletThread::workerBackingThread()
 {
-    return *BackingThreadHolder::instance().thread();
+    return *BackingThreadHolder::instance()->thread();
+}
+
+void collectAllGarbageOnThread(WaitableEvent* doneEvent)
+{
+    blink::ThreadState::current()->collectAllGarbage();
+    doneEvent->signal();
+}
+
+void AbstractAnimationWorkletThread::collectAllGarbage()
+{
+    DCHECK(isMainThread());
+    WaitableEvent doneEvent;
+    BackingThreadHolder* instance = BackingThreadHolder::instance();
+    if (!instance)
+        return;
+    instance->thread()->backingThread().postTask(BLINK_FROM_HERE, crossThreadBind(&collectAllGarbageOnThread, crossThreadUnretained(&doneEvent)));
+    doneEvent.wait();
 }
 
 void AbstractAnimationWorkletThread::ensureSharedBackingThread()

third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.h

@@ -29,6 +29,8 @@ public:
 
     bool shouldAttachThreadDebugger() const override { return false; }
 
+    static void collectAllGarbage();
+
     static void ensureSharedBackingThread();
     static void createSharedBackingThreadForTest();
 

third_party/WebKit/Source/web/WebLeakDetector.cpp

@@ -36,6 +36,7 @@
 #include "core/inspector/InstanceCounters.h"
 #include "core/workers/InProcessWorkerMessagingProxy.h"
 #include "core/workers/WorkerThread.h"
+#include "modules/compositorworker/AbstractAnimationWorkletThread.h"
 #include "platform/Timer.h"
 #include "public/web/WebFrame.h"
 #include "web/WebLocalFrameImpl.h"
@@ -105,6 +106,7 @@ void WebLeakDetectorImpl::prepareForLeakDetection(WebFrame* frame)
 void WebLeakDetectorImpl::collectGarbageAndReport()
 {
     V8GCController::collectAllGarbageForTesting(V8PerIsolateData::mainThreadIsolate());
+    AbstractAnimationWorkletThread::collectAllGarbage();
     // Note: Oilpan precise GC is scheduled at the end of the event loop.
 
     // Task queue may contain delayed object destruction tasks.
@@ -122,6 +124,7 @@ void WebLeakDetectorImpl::delayedGCAndReport(TimerBase*)
     // The third GC is necessary for cleaning up Document after worker object died.
 
     V8GCController::collectAllGarbageForTesting(V8PerIsolateData::mainThreadIsolate());
+    AbstractAnimationWorkletThread::collectAllGarbage();
     // Note: Oilpan precise GC is scheduled at the end of the event loop.
 
     // Inspect counters on the next event loop.