Fix ElfCoreDumpTest.ValidCoreFile unit test.

Fix ElfCoreDumpTest.ValidCoreFile unit test.

The ElfCoreDumpTest.ValidCoreFile unit test assumed that the number of
NT_FPREGSET / NT_PRXFPREG notes in the core dump file equals to the number of
threads of the crashed process. This assumption isn't always true as the kernel
skips filling the NT_FPREGSET / NT_PRXFPREG note of a thread if the FPU state
isn't available. The kernel indicates the availability of NT_FPREGSET /
NT_PRXFPREG via the pr_fpvalid field of the NT_PRSTATUS note. This CL modifies
the ElfCoreDumpTest.ValidCoreFile unit test to verify the number of NT_FPREGSET
and NT_PRXFPREG notes based on the pr_fpvalid field of the NT_PRSTATUS notes.

BUG=577
TEST=Run unit tests on x86 and x86_64 Linux platform.
R=vapier@chromium.org

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1303

[vapier]

lgtm

i've verified it works on 2.6.32/3.6/3.9/3.11/3.14

versions 2.6.18/2.6.21 failed for an unrelated reason, but not sure we care
enough to figure out why

[Ben Chan]

Committed patchset #1 manually as r1303 (presubmit successful).