Fix an integer overflow in CStretchEngine constructor

Fix an integer overflow in CStretchEngine constructor

When the source bitmap's width and height are large,
the multiplication could easily overflow a signed integer.
Change to use 'long long' type for calculation to avoid that.

BUG=chromium:635663
Committed: https://pdfium.googlesource.com/pdfium/+/229d05df5bc5deb3890b26b614113c25d9b6935e

[Wei Li, 2016-08-11 23:19:02]

The CQ bit was checked by weili@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-11 23:19:09]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-11 23:31:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-11 23:31:07]

Dry run: This issue passed the CQ dry run.

[Wei Li, 2016-08-11 23:36:14]

weili@chromium.org changed reviewers:
+ dsinclair@chromium.org

[Wei Li, 2016-08-11 23:36:15]

pls review, thanks

[dsinclair, 2016-08-12 02:43:39]

The CQ bit was checked by dsinclair@chromium.org

[dsinclair, 2016-08-12 02:43:39]

lgtm

[commit-bot: I haz the power, 2016-08-12 02:43:42]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-12 02:44:04]

Description was changed from

==========
Fix an integer overflow in CStretchEngine constructor

When the source bitmap's width and height are large,
the multiplication could easily overflow a signed integer.
Change to use 'long long' type for calculation to avoid that.

BUG=chromium:635663
==========

to

==========
Fix an integer overflow in CStretchEngine constructor

When the source bitmap's width and height are large,
the multiplication could easily overflow a signed integer.
Change to use 'long long' type for calculation to avoid that.

BUG=chromium:635663

Committed:
https://pdfium.googlesource.com/pdfium/+/229d05df5bc5deb3890b26b614113c25d9b6...
==========

[commit-bot: I haz the power, 2016-08-12 02:44:05]

Committed patchset #1 (id:1) as
https://pdfium.googlesource.com/pdfium/+/229d05df5bc5deb3890b26b614113c25d9b6...