Add output scale factor command line parameter to pdfium_test.

Add output scale factor command line parameter to pdfium_test.

It turns out that pdfium rendering takes some significantly different paths
when the output bitmap size is the same as the document size, since it can
avoid work in that case. For example, to reproduce the referenced bug, a scale
factor less than 1.0 is required, so we add a parameter to let pdfium_test
cover that case.

BUG=451265
R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/daa2e84dfca2f1cf39e064bd9ad6ee3e2cd70825

[Tom Sepez, 2015-01-29 19:49:59]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-01-29 19:50:00]

Lei, please review.

[Lei Zhang, 2015-01-29 22:15:18]

lgtm, though there's a few typos in the CL description.

https://codereview.chromium.org/861203003/diff/1/samples/pdfium_test.cc
File samples/pdfium_test.cc (right):

https://codereview.chromium.org/861203003/diff/1/samples/pdfium_test.cc#newco...
samples/pdfium_test.cc:13: #include <sstream>
nit: alphabetical order

https://codereview.chromium.org/861203003/diff/1/samples/pdfium_test.cc#newco...
samples/pdfium_test.cc:451: std::stringstream(options.scale_factor_as_string) >>
scale;
Is this the preferred way to do StringToDouble() in the absense of
string_number_conversions.h? What happens when the input is invalid?

[Tom Sepez, 2015-01-29 23:37:19]

> Is this the preferred way to do StringToDouble() in the absense of
> string_number_conversions.h? What happens when the input is invalid?
Not sure what the ideal method would be. Since this is a "sample" program, I
wanted to do this in the most vanilla C++ way possible, which I thought this
was.  If input is invalid, |scale| remains unchanged, so I've changed this to
pre-initialize it to 1.0.

[Tom Sepez, 2015-01-29 23:37:32]

https://codereview.chromium.org/861203003/diff/1/samples/pdfium_test.cc
File samples/pdfium_test.cc (right):

https://codereview.chromium.org/861203003/diff/1/samples/pdfium_test.cc#newco...
samples/pdfium_test.cc:13: #include <sstream>
On 2015/01/29 22:15:18, Lei Zhang wrote:
> nit: alphabetical order

Done.

[Lei Zhang, 2015-01-29 23:40:56]

Ok, sounds good.

s/comand/command/
s/takse/takes/
s/referened/referenced/

[Tom Sepez, 2015-01-29 23:44:42]

Committed patchset #2 (id:20001) manually as
daa2e84dfca2f1cf39e064bd9ad6ee3e2cd70825 (presubmit successful).