Move ownership of the TextResourceDecoder to DecodedDataDocumentParser

Move ownership of the TextResourceDecoder to DecodedDataDocumentParser

This moves the Document's reference to the decoder to the parser. The
parser informs the document of changes in the encoding as well as two
bits indicating if the encoding was determined heuristically (to set up
the decoder properly for child frames) and if the decoder has encountered
any decoding errors (to generate errors for XML documents).

BUG=277886

[jamesr, 2013-08-30 22:44:48]

Document::DocumentEncodingData is really ugly in this patch, but I think the
rest is in pretty good shape so I'd like to get feedback on that.  For the data
bundle I think if I just put it in its own header and provide better ways to
build it (maybe some better constructors or builders) it'll be OK.  I also don't
think DecodedDataDocumentParser is the right place for this to live long-term
but just moving it out of Document is already a big patch.

[abarth-chromium, 2013-08-30 22:50:38]

https://codereview.chromium.org/23455024/diff/1/Source/core/dom/DecodedDataDo...
File Source/core/dom/DecodedDataDocumentParser.cpp (right):

https://codereview.chromium.org/23455024/diff/1/Source/core/dom/DecodedDataDo...
Source/core/dom/DecodedDataDocumentParser.cpp:109:
document()->setEncoding(encodingData);
This happens for every call to appendBytes?  We can probably do better than
that.

https://codereview.chromium.org/23455024/diff/1/Source/core/dom/DecodedDataDo...
Source/core/dom/DecodedDataDocumentParser.cpp:133:
document()->setEncoding(encodingData);
Copy/paste code makes me a sad panda.

https://codereview.chromium.org/23455024/diff/1/Source/core/dom/Document.cpp
File Source/core/dom/Document.cpp (right):

https://codereview.chromium.org/23455024/diff/1/Source/core/dom/Document.cpp#...
Source/core/dom/Document.cpp:1135: setEncoding(data);
Won't this get spammed over the next time we get a chunk of data from the
network?

https://codereview.chromium.org/23455024/diff/1/Source/core/loader/DocumentWr...
File Source/core/loader/DocumentWriter.cpp (right):

https://codereview.chromium.org/23455024/diff/1/Source/core/loader/DocumentWr...
Source/core/loader/DocumentWriter.cpp:102:
m_parser->asDecodedDataDocumentParser()->setDecoder(m_decoder);
Maybe setDecoder should be defined on the same interface as needsDecoder?  Then
you wouldn't need this dynamic cast.