Prevent segfault if file cannot be opened when --ll_prof is used.

TEST=

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/16107002

Patch from Dusan Milosavljevic <Dusan.Milosavljevic@rt-rk.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14889 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/platform-linux.cc

@@ -591,6 +591,10 @@ void OS::SignalCodeMovingGC() {
   // kernel log.
   int size = sysconf(_SC_PAGESIZE);
   FILE* f = fopen(FLAG_gc_fake_mmap, "w+");
+  if (f == NULL) {
+    OS::PrintError("Failed to open %s\n", FLAG_gc_fake_mmap);
+    OS::Abort();
+  }
   void* addr = mmap(OS::GetRandomMmapAddr(),
                     size,
                     PROT_READ | PROT_EXEC,

src/platform-openbsd.cc

@@ -344,6 +344,10 @@ void OS::SignalCodeMovingGC() {
   // kernel log.
   int size = sysconf(_SC_PAGESIZE);
   FILE* f = fopen(FLAG_gc_fake_mmap, "w+");
+  if (f == NULL) {
+    OS::PrintError("Failed to open %s\n", FLAG_gc_fake_mmap);
+    OS::Abort();
+  }
   void* addr = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_PRIVATE,
                     fileno(f), 0);
   ASSERT(addr != MAP_FAILED);