Exit early if decompressed size exceeds OTSStream's size limit

[fred-wang]

Currently we are exiting early if decompressed size exceeds
OTS_MAX_DECOMPRESSED_FILE_SIZE=300MB but some callers may actually set a
smaller limit. For example, Chromium uses 30MB [1] and its internal
fuzzer 256kB [2]. Firefox uses a limit of 256MB [3].

[1] https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/platform/fonts/web_font_decoder.cc;l=155;drc=5863e513ede6d1f7e9a060f13635fd3916a2183c
[2] https://source.chromium.org/chromium/chromium/src/+/main:third_party/ots/fuzz/ots_fuzzer.cc;l=11;drc=efffce8e2a6da2d2295472ed24ef040e0bf4ea14
[3] https://searchfox.org/mozilla-central/rev/3e1a721bce1da3ae04675539b39a4e95b25a046d/gfx/thebes/gfxOTSUtils.h#28

[fred-wang]

cc @khaledhosny @jfkthame @drott

[fred-wang]

@jfkthame gfxOTSExpandingMemoryStream will need a

      size_t SizeLimit() override { return m_Limit; }

if this is taken.

[khaledhosny]

I don’t like the fact that we now have two different limits, and one is configurable and the other is not.

[fred-wang]

To be clear, I believe we already have two limits:

1. OTS_MAX_DECOMPRESSED_FILE_SIZE which is configurable at build time as a #ifdef.
2. OTSStream's (well MemoryStream/ExpandingMemoryStream) limit which is specified at runtime in the constructor (so more easily configurable for third party)

So this commit is only fixing the process functions to take into account (2), which is the limit configuration used by Firefox/Chromium.

What do you suggest?

[khaledhosny]

I’d rename it size().

[fred-wang]

Done. Existing methods in OTSStream seemed to use CamelCase but I see that the trival one chksum() does not.

[khaledhosny]

On a second thought, it makes sense.

[fred-wang]

@khaledhosny thanks!

[fred-wang]

mmh, I'm getting this kind of warnings when trying to port to chromium, so I guess we should use override everywhere

../../third_party/ots/src/include/ots-memory-stream.h:23:16: error: 'WriteRaw' overrides a member function but is not marked 'override' [-Werror,-Winconsistent-missing-override]
virtual bool WriteRaw(const void *data, size_t length) {
^