sys_info_linux: positive return value of MaxSharedMemorySize for 32-bit build on 64-bit host.

base/sys_info.h

Index: base/sys_info.h
diff --git a/base/sys_info.h b/base/sys_info.h
index 660343d06f76831b2f6dceff35cce4bb40e212c0..654d6945a34ba26250356f5b21caa5c8a16f6112 100644
--- a/base/sys_info.h
+++ b/base/sys_info.h
@@ -94,7 +94,7 @@ class BASE_EXPORT SysInfo {
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
   // Returns the maximum SysV shared memory segment size, or zero if there is no
   // limit.
-  static size_t MaxSharedMemorySize();
+  static uint64 MaxSharedMemorySize();
 #endif  // defined(OS_POSIX) && !defined(OS_MACOSX)
 
 #if defined(OS_CHROMEOS)