Speed up fix for expando-loss conformance test.

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

Index: third_party/WebKit/Source/modules/webgl/WebGLObject.h
diff --git a/third_party/WebKit/Source/modules/webgl/WebGLObject.h b/third_party/WebKit/Source/modules/webgl/WebGLObject.h
index 6fe0442298e365e767876869325286932dc2abce..2a8011327db1f103dcd9d0c0ef8eaf7a069684cd 100644
--- a/third_party/WebKit/Source/modules/webgl/WebGLObject.h
+++ b/third_party/WebKit/Source/modules/webgl/WebGLObject.h
@@ -56,6 +56,18 @@ GLuint objectNonZero(const T* object)
     return result;
 }
 
+// TODO(kbr): v8::Persistent doesn't auto-reset in its destructor,
+// which wreaks havoc when they're embedded in Oilpan objects even if
+// they use GarbageCollectedFinalized. The first V8 GC after the
+// Oilpan object is reclaimed will reset the cell in the
+// v8::Persistent, scribbling over the Oilpan heap. If v8::Persistents
+// are ever embedded in Oilpan objects, they must use
+// CopyablePersistentTraits to pick up the kResetInDestructor = true
+// setting. This alias template ensures correct usage, but ideally,
+// these persistent caches would not be necessary. crbug.com/611864
+template <typename T>
+using V8CopyablePersistent = v8::Persistent<T, v8::CopyablePersistentTraits<T>>;

[haraken, 2016/05/15 09:18:46]

Instead you should use ScopedPersistent. Then ScopedPersistent's destructor
resets the underlying persistent handle, which will solve the problem.

+
 class WebGLObject : public GarbageCollectedFinalized<WebGLObject>, public ScriptWrappable {
 public:
     virtual ~WebGLObject();