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

base/sys_info_ios.mm

Index: base/sys_info_ios.mm
diff --git a/base/sys_info_ios.mm b/base/sys_info_ios.mm
index 49d618c416f7a42780b96c847639ffc4388d0fb8..324bef6b839d9174d9951046f67ad7510c246fe6 100644
--- a/base/sys_info_ios.mm
+++ b/base/sys_info_ios.mm
@@ -16,6 +16,12 @@
 
 namespace base {
 
+bool SysInfo::HasSeekPenalty(const FilePath& path, bool* has_seek_penalty) {
+  // Find a case where this is incorrect and dbeam@ will buy you a beer.
+  *has_seek_penalty = false;
+  return true;
+}
+
 // static
 std::string SysInfo::OperatingSystemName() {
   static dispatch_once_t get_system_name_once;