Fix SourceBuffer.timestampOffset setter behavior for invalid values.

Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 157 matching lines @@
     return TimeRanges::create(m_webSourceBuffer->buffered());
 }
 
 double SourceBuffer::timestampOffset() const
 {
     return m_timestampOffset;
 }
 
 void SourceBuffer::setTimestampOffset(double offset, ExceptionState& exceptionState)
 {
+    // Enforce throwing an exception on restricted double values.
+    if (!std::isfinite(offset)) {
+        exceptionState.throwDOMException(TypeMismatchError, ExceptionMessages::notAFiniteNumber(offset));

[sof, 2014/03/22 07:51:23]

This isn't quite right per WebIDL, infinities and NaN should throw TypeError --

  http://heycam.github.io/webidl/#es-double (4.2.14.2)

The old DOM exception TYPE_MISMATCH_ERR (TypeMismatchError) is preferably
avoided these days.

+        return;
+    }
+
     // Section 3.1 timestampOffset attribute setter steps.
     // 1. Let new timestamp offset equal the new value being assigned to this attribute.
     // 2. If this object has been removed from the sourceBuffers attribute of the parent media source, then throw an
     //    InvalidStateError exception and abort these steps.
     // 3. If the updating attribute equals true, then throw an InvalidStateError exception and abort these steps.
     if (throwExceptionIfRemovedOrUpdating(isRemoved(), m_updating, exceptionState))
         return;
 
     // 4. If the readyState attribute of the parent media source is in the "ended" state then run the following steps:
     // 4.1 Set the readyState attribute of the parent media source to "open"
@@ skipping 515 matching lines @@
     appendStreamDone(false);
 }
 
 void SourceBuffer::trace(Visitor* visitor)
 {
     visitor->trace(m_source);
     visitor->trace(m_stream);
 }
 
 } // namespace WebCore