Remove WebGLObject maps from WebGLRenderingContextBase and WebGLContextGroup.

third_party/WebKit/Source/modules/webgl/WebGLContextGroup.cpp

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 #include "modules/webgl/WebGLContextGroup.h"
 
-#include "modules/webgl/WebGLSharedObject.h"
-
 namespace blink {
 
-PassRefPtr<WebGLContextGroup> WebGLContextGroup::create() {
-  RefPtr<WebGLContextGroup> contextGroup = adoptRef(new WebGLContextGroup());
-  return contextGroup.release();
-}
-
-WebGLContextGroup::WebGLContextGroup() {}
-
-WebGLContextGroup::~WebGLContextGroup() {
-  detachAndRemoveAllObjects();
-}
+WebGLContextGroup::WebGLContextGroup() : m_numberOfContextLosses(0) {}
 
 gpu::gles2::GLES2Interface* WebGLContextGroup::getAGLInterface() {
   ASSERT(!m_contexts.isEmpty());
+  // TODO(kbr): is it guaranteed that we won't return null here
+  // because the WeakMember was nulled out but its entry wasn't
+  // removed from the HeapHashSet?

[Ken Russell (switch to Gerrit), 2016/12/02 09:58:48]

haraken@ and sigbjornf@: could you answer this question?

[haraken, 2016/12/02 10:14:34]

The weak processing removes the dead entry from the HashSet. So it's guaranteed
that this does not return null.

[sof, 2016/12/02 10:39:06]

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/wtf/HashTable....
is where this happens as part of weak reference processing during GC.

[Ken Russell (switch to Gerrit), 2016/12/02 20:38:49]

Thanks for the feedback. I'll include this information in the comment.

   return (*m_contexts.begin())->contextGL();
 }
 
 void WebGLContextGroup::addContext(WebGLRenderingContextBase* context) {
   m_contexts.add(context);
 }
 
-void WebGLContextGroup::removeContext(WebGLRenderingContextBase* context) {
-  // We must call detachAndRemoveAllObjects before removing the last context.
-  if (m_contexts.size() == 1 && m_contexts.contains(context))
-    detachAndRemoveAllObjects();
-
-  m_contexts.remove(context);
-}
-
-void WebGLContextGroup::removeObject(WebGLSharedObject* object) {
-  m_groupObjects.remove(object);
-}
-
-void WebGLContextGroup::addObject(WebGLSharedObject* object) {
-  m_groupObjects.add(object);
-}
-
-void WebGLContextGroup::detachAndRemoveAllObjects() {
-  while (!m_groupObjects.isEmpty()) {
-    (*m_groupObjects.begin())->detachContextGroup();
-  }
-}
-
 void WebGLContextGroup::loseContextGroup(
     WebGLRenderingContextBase::LostContextMode mode,
     WebGLRenderingContextBase::AutoRecoveryMethod autoRecoveryMethod) {
-  // Detach must happen before loseContextImpl, which destroys the
-  // GraphicsContext3D and prevents groupObjects from being properly deleted.
-  detachAndRemoveAllObjects();
-
+  ++m_numberOfContextLosses;
   for (WebGLRenderingContextBase* const context : m_contexts)
     context->loseContextImpl(mode, autoRecoveryMethod);
 }
 
+uint32_t WebGLContextGroup::numberOfContextLosses() const {
+  return m_numberOfContextLosses;
+}
+
+DEFINE_TRACE_WRAPPERS(WebGLContextGroup) {
+  // TODO(kbr, mlippautz): need to use the manual write barrier since we

[Ken Russell (switch to Gerrit), 2016/12/02 09:58:48]

mlippautz: am I correct in my thinking here?

+  // need to use weak members, but no such TraceWrapperMember exists yet.
+  for (auto context : m_contexts) {
+    visitor->traceWrappersWithManualWriteBarrier(context);
+  }
+}
+
 }  // namespace blink