Fix SourceBuffer.timestampOffset setter behavior for invalid values.

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 c0d64a19a4fbc826d2c88a0836020271ba4cc64e..87c6cf1dc05fbe9d1903a4b3021d73d0fc56ec22 100644
--- a/Source/modules/mediasource/SourceBuffer.cpp
+++ b/Source/modules/mediasource/SourceBuffer.cpp
@@ -175,6 +175,12 @@ double SourceBuffer::timestampOffset() const
 
 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