Oilpan: have the media element safely close its MediaSource.

Source/modules/mediasource/SourceBuffer.cpp

Index: Source/modules/mediasource/SourceBuffer.cpp
diff --git a/Source/modules/mediasource/SourceBuffer.cpp b/Source/modules/mediasource/SourceBuffer.cpp
index 741e25c67df41187718a190c119e5af95408a4ec..12031d31514362be45a4bd1ed60245126797d2c8 100644
--- a/Source/modules/mediasource/SourceBuffer.cpp
+++ b/Source/modules/mediasource/SourceBuffer.cpp
@@ -105,9 +105,14 @@ SourceBuffer::SourceBuffer(PassOwnPtr<WebSourceBuffer> webSourceBuffer, MediaSou
 
 SourceBuffer::~SourceBuffer()
 {
+    // Oilpan: a SourceBuffer might be finalized without having been
+    // explicitly removed first, hence the asserts below will not
+    // hold.
+#if !ENABLE(OILPAN)
     ASSERT(isRemoved());
     ASSERT(!m_loader);
     ASSERT(!m_stream);
+#endif
 }
 
 const AtomicString& SourceBuffer::segmentsKeyword()