Replace FilePath declaration with file_path.h include

Fixes a clang error.  Also use "base::FilePath" since FilePath has been
moved to the base namespace.

BUG=chromium-os:39046
TEST=The following command passes:
USE="chrome_internal" CFLAGS="-clang -print-cmdline"
CXXFLAGS="-clang -print-cmdline" emerge-x86-alex crash-reporter

Change-Id: I7da82093c5685b5b556cba971b1e1b14ac0f59c4
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/43577
Reviewed-by: Ben Chan <benchan@chromium.org>
diff --git a/crash_reporter/unclean_shutdown_collector_test.cc b/crash_reporter/unclean_shutdown_collector_test.cc
index 8adb4d3..1bb0c94 100644
--- a/crash_reporter/unclean_shutdown_collector_test.cc
+++ b/crash_reporter/unclean_shutdown_collector_test.cc
@@ -20,6 +20,7 @@
 static const char kTestSuspended[] = "test/suspended";
 static const char kTestUnclean[] = "test/unclean";
 
+using base::FilePath;
 using ::chromeos::FindLog;
 
 void CountCrash() {