Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/modules/mediasource/WebKitSourceBuffer.cpp

Index: Source/modules/mediasource/WebKitSourceBuffer.cpp
diff --git a/Source/modules/mediasource/WebKitSourceBuffer.cpp b/Source/modules/mediasource/WebKitSourceBuffer.cpp
index 992f11ebdbc2e194aaf46005bfee3579c8ec0ca8..fa82ac6c118ab30a7fc3426231b03a012401edcc 100644
--- a/Source/modules/mediasource/WebKitSourceBuffer.cpp
+++ b/Source/modules/mediasource/WebKitSourceBuffer.cpp
@@ -79,7 +79,7 @@ PassRefPtr<TimeRanges> WebKitSourceBuffer::buffered(ExceptionState& exceptionSta
     // 1. If this object has been removed from the sourceBuffers attribute of the parent media source then throw an
     //    InvalidStateError exception and abort these steps.
     if (throwExceptionIfRemoved(isRemoved(), exceptionState))
-        return 0;
+        return nullptr;
 
     // 2. Return a new static normalized TimeRanges object for the media segments buffered.
     return TimeRanges::create(m_webSourceBuffer->buffered());