Disable JBIG2 cache; prevent data corruption - try 2.

Disable JBIG2 cache; prevent data corruption - try 2.

Also change CJBig2_SymbolDict::DeepCopy() to return a unique_ptr to
prevent a potential leak if the cache size was 0.

BUG=pdfium:207
R=tsepez@chromium.org, jbreiden@google.com

Committed: https://pdfium.googlesource.com/pdfium/+/fd12ec5584d9a17f310a2c0c408a438ef3b1ce63

[Lei Zhang, 2015-10-04 06:23:08]

If I set |kSymbolDictCacheMaxSize| to 0, I get compiler warnings.

[Tom Sepez, 2015-10-04 23:57:48]

https://codereview.chromium.org/1374633004/diff/1/core/src/fxcodec/jbig2/JBig...
File core/src/fxcodec/jbig2/JBig2_Context.cpp (right):

https://codereview.chromium.org/1374633004/diff/1/core/src/fxcodec/jbig2/JBig...
core/src/fxcodec/jbig2/JBig2_Context.cpp:28: #define DISABLE_SYMBOL_CACHE 1
nit: some reason why we we need the "1", instead of just defining it?

[Lei Zhang, 2015-10-05 00:38:26]

https://codereview.chromium.org/1374633004/diff/1/core/src/fxcodec/jbig2/JBig...
File core/src/fxcodec/jbig2/JBig2_Context.cpp (right):

https://codereview.chromium.org/1374633004/diff/1/core/src/fxcodec/jbig2/JBig...
core/src/fxcodec/jbig2/JBig2_Context.cpp:28: #define DISABLE_SYMBOL_CACHE 1
On 2015/10/04 23:57:48, Tom Sepez wrote:
> nit: some reason why we we need the "1", instead of just defining it?

Done.

[Tom Sepez, 2015-10-05 16:36:23]

lgtm

[Lei Zhang, 2015-10-05 17:16:28]

Committed patchset #2 (id:20001) manually as
fd12ec5584d9a17f310a2c0c408a438ef3b1ce63 (presubmit successful).