base: "implement" seek time detection for iOS/Android and add more stubs.

base/sys_info_openbsd.cc

Index: base/sys_info_openbsd.cc
diff --git a/base/sys_info_openbsd.cc b/base/sys_info_openbsd.cc
index edbb2c9d86c305cdb605051d6165770e8ea3a28c..68d2ea14886ff832ab00d3dc88e78c90c10aba52 100644
--- a/base/sys_info_openbsd.cc
+++ b/base/sys_info_openbsd.cc
@@ -48,6 +48,10 @@ int64 SysInfo::AmountOfAvailablePhysicalMemory() {
   return AmountOfMemory(_SC_AVPHYS_PAGES);
 }
 
+bool SysInfo::HasSeekPenalty(const FilePath& path, bool* has_seek_penalty) {
+  return false;
+}
+
 // static
 size_t SysInfo::MaxSharedMemorySize() {
   int mib[] = { CTL_KERN, KERN_SHMINFO, KERN_SHMINFO_SHMMAX };