Add ability to convert FragmentedSharedBuffer to CMBlockBuffer

[Jean-Yves Avenard [:jya]]

Sub-task of bug 236754.

We can simplify the rewrite of SourceBufferParserWebM by using SharedBuffers instead.

Once we have built the SharedBuffer, we would want an easy way to convert it into a CMBlockBuffer without allocating memory or performing any copies.

[Radar WebKit Bug Importer]

<rdar://problem/89338447>

[Jean-Yves Avenard [:jya]]

Created attachment 452960 [details]
Patch

[Jean-Yves Avenard [:jya]]

Created attachment 453063 [details]
Patch

[Jean-Yves Avenard [:jya]]

Comment on attachment 453063 [details]
Patch

Unrelated failure, that code path isn't even used yet.

[Jean-Yves Avenard [:jya]]

Created attachment 453093 [details]
Patch

[Jer Noble]

Comment on attachment 453093 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453093&action=review

> Source/WebCore/platform/SharedBuffer.cpp:162
> +    if (element->segment->size() - offsetInSegment >= length)

Is it possible for element->segment->size() to be < offsetInSegment? If not, maybe an ASSERT() that states such?

[Jean-Yves Avenard [:jya]]

Comment on attachment 453093 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=453093&action=review

>> Source/WebCore/platform/SharedBuffer.cpp:162
>> +    if (element->segment->size() - offsetInSegment >= length)
> 
> Is it possible for element->segment->size() to be < offsetInSegment? If not, maybe an ASSERT() that states such?

No, it's not possible. unless getSegmentForPosition is buggy and it's not :)

[Jean-Yves Avenard [:jya]]

Created attachment 454038 [details]
Patch

[EWS]

Committed r290968 (248147@main): <https://commits.webkit.org/248147@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 454038 [details].