Eliminate build warnings in base/ for Android x64

base/os_compat_android.cc

Index: base/os_compat_android.cc
===================================================================
--- base/os_compat_android.cc	(revision 254431)
+++ base/os_compat_android.cc	(working copy)
@@ -41,8 +41,8 @@
 // We replicate the behaviour of timegm() when the result overflows time_t.
 time_t timegm(struct tm* const t) {
   // time_t is signed on Android.
-  static const time_t kTimeMax = ~(1 << (sizeof(time_t) * CHAR_BIT - 1));
-  static const time_t kTimeMin = (1 << (sizeof(time_t) * CHAR_BIT - 1));
+  static const time_t kTimeMax = ~(1L << (sizeof(time_t) * CHAR_BIT - 1));
+  static const time_t kTimeMin = (1L << (sizeof(time_t) * CHAR_BIT - 1));
   time64_t result = timegm64(t);
   if (result < kTimeMin || result > kTimeMax)
     return -1;