log_unit_tests: fix unittest delete

The code uses "new[...]" but then uses "delete" instead of "delete[]".
This is why ASAN has been barfing on us:
==15739==ERROR: AddressSanitizer: alloc-dealloc-mismatch (operator new [] vs operator delete) on 0x60300000eb00
    #0 0x4774cb in operator delete(void*) (.../log_unit_test+0x4774cb)
    #1 0x49be55 in (anonymous namespace)::ValidateEventFileContents(std::string const&, std::string const&) .../log_unit_tests.cc:96
    ...
0x60300000eb00 is located 0 bytes inside of 23-byte region [0x60300000eb00,0x60300000eb17)
allocated by thread T0 here:
    #0 0x4770db in operator new[](unsigned long) (.../log_unit_test+0x4770db)
    ...
SUMMARY: AddressSanitizer: alloc-dealloc-mismatch ??:0 operator delete(void*)

BUG=chromium:335808
TEST=`FEATURES=test emerge-amd64-generic-asan bootstat` now passes

Change-Id: I0cdfa4d57647cc7ef6aa5469544f34041a5b0124
Reviewed-on: https://chromium-review.googlesource.com/196473
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed