Fix free entry handling for cross reference v4 reading.

Fix free entry handling for cross reference v4 reading.

While reading free entries in v4 cross reference table, changing the
start_objnum caused crossref table built wrong.

BUG=569795
R=jun_fang@foxitsoftware.com, thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/c89cd979fb8654d85b822909cba9263d5f13760c

[Wei Li, 2015-12-15 04:22:02]

weili@chromium.org changed reviewers:
+ jun_fang@foxitsoftware.com, thestig@chromium.org

[Wei Li, 2015-12-15 04:22:03]

Please be extra careful while reviewing the code. The root cause is the line
551--updating start_objnum. I am not sure whether there is any corner case
relying on this line. And also the other part of the deleted code seems like an
noop to me.

I added four examples to test the change. The last two would fail on original
code (without this change). 

thanks.

[jun_fang, 2015-12-15 12:20:21]

On 2015/12/15 04:22:03, Wei wrote:
> Please be extra careful while reviewing the code. The root cause is the line
> 551--updating start_objnum. I am not sure whether there is any corner case
> relying on this line. And also the other part of the deleted code seems like
an
> noop to me.
> 
> I added four examples to test the change. The last two would fail on original
> code (without this change). 
> 
> thanks.

LGTM. Thanks!

[Lei Zhang, 2015-12-15 22:53:58]

lgtm

[Wei Li, 2015-12-16 00:08:54]

Description was changed from

==========
Fix free entry handling for cross reference v4 reading.

While reading free entries in v4 cross reference table, changing the
start_objnum caused crossref table built wrong.

BUG=569795
==========

to

==========
Fix free entry handling for cross reference v4 reading.

While reading free entries in v4 cross reference table, changing the
start_objnum caused crossref table built wrong.

BUG=569795
R=jun_fang@foxitsoftware.com, thestig@chromium.org

Committed:
https://pdfium.googlesource.com/pdfium/+/c89cd979fb8654d85b822909cba9263d5f13...
==========

[Wei Li, 2015-12-16 00:08:57]

Committed patchset #1 (id:1) manually as
c89cd979fb8654d85b822909cba9263d5f13760c (presubmit successful).