Add optional coverage flags to build

This CL allows generating coverage information for the source files. By adding
use_coverage=true to the GN build settings clang will generate .gcno files for
each source file and executing the binary will generate a .gcda file for
each source file.

Those files can then be processed by llvm-cov to generate .gcov reports for each
source file.

i.e. (assuming use_coverage=true is set for out/coverage)
  * ninja -C out/coverage pdfium_unittests
  * cd out/coverage
  * find obj -name "*.o" -exec llvm-cov -af -stats {} > d.out \;

There should now be .gcov files for each source file in the out/coverage
directory.

Note, llvm-gcov may have a different name or syntax on your machine.

Change-Id: I7379579f5f20a5b8b2f3a3b409b868bba4b4d74d
Reviewed-on: https://pdfium-review.googlesource.com/2216
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

0 files changed, 0 insertions, 0 deletions