[Oilpan] Fix wrong usage of HashSet<WebGLSharedObject*>

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

Index: third_party/WebKit/Source/modules/webgl/WebGLContextGroup.h
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLContextGroup.h b/third_party/WebKit/Source/modules/webgl/WebGLContextGroup.h
index c1244fc32b04b5ac0531def6f75cbdcbbe0b48fd..85f6a703ee13bd9ebc06a2405a5974b0d42584dd 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLContextGroup.h
+++ b/third_party/WebKit/Source/modules/webgl/WebGLContextGroup.h
@@ -72,7 +72,7 @@ private:
     // the set of WebGLRenderingContextBase contexts becomes empty.
     HashSet<WebGLRenderingContextBase*> m_contexts;
     GC_PLUGIN_IGNORE("http://crbug.com/516610")
-    HashSet<WebGLSharedObject*> m_groupObjects;
+    WillBeHeapHashSet<RawPtrWillBeUntracedMember<WebGLSharedObject>> m_groupObjects;

[haraken, 2015/10/22 02:27:04]

This must be
WillBePersistentHeapHashSet<RawPtrWillBeUntracedMember<WebGLSharedObject>>
because WebGLContextGroup is an off-heap object.

yutak@: It would be great if the plugin can detect the error.

Not related to this CL, I noticed one thing.

  class X : public GarbageCollected<X> {
    DEFINE_INLINE_TRACE() { }
    HeapVector<UntracedMember<Y>> m_vec;
  };

I was thinking that the above code is correct but isn't. We must trace the
m_vec. Otherwise, the backing storage of the HeapVector is gone. In other words,
the correct code would be:

  class X : public GarbageCollected<X> {
    DEFINE_INLINE_TRACE() {
      visitor->trace(m_vec);  // This traces the backing storage of the
HeapVector but doesn't trace the untraced members in the vector.
    }
    HeapVector<UntracedMember<Y>> m_vec;
  };

peria@: Can we add more test cases about HeapVector<UntracedMember> and
HeapHashSet<UntracedMember> to HeapTest.cpp?

[peria, 2015/10/22 02:38:10]

Oops, this was my mistake, but I think this should be
  HashSet<RawPtrWillBeUntracedMember<WebGLSharedObject>>
so, yes, the situation you noticed was what I made this CL wrong.
I think HeapVector<UntracedMember<Y>> should not be allowed.

[haraken, 2015/10/22 03:55:42]

OK. Either way, it's better to have more tests in HeapTest.cpp.

 };
 
 } // namespace blink