Remove trivially-true DEBUG_CHECKs in safe_sprintf.cc

There are some DEBUG_CHECKs here verifying that a size_t is >= 0. Since a size_t is unsigned, these are trivially true and with the default warning settings for CrOS builds, the warning generated here will cause a build failure.

BUG=424334
TEST=ensure existing builds pass

Review URL: https://codereview.chromium.org/642263006

Cr-Commit-Position: refs/heads/master@{#300025}

base/strings/safe_sprintf.cc

@@ -176,8 +176,7 @@ class Buffer {
   // overflowed |size_|) at any time during padding.
   inline bool Pad(char pad, size_t padding, size_t len) {
     DEBUG_CHECK(pad);
-    DEBUG_CHECK(padding >= 0 && padding <= kSSizeMax);
-    DEBUG_CHECK(len >= 0);
+    DEBUG_CHECK(padding <= kSSizeMax);
     for (; padding > len; --padding) {
       if (!Out(pad)) {
         if (--padding) {
@@ -283,7 +282,6 @@ bool Buffer::IToASCII(bool sign, bool upcase, int64_t i, int base,
   DEBUG_CHECK(base <= 16);
   DEBUG_CHECK(!sign || base == 10);
   DEBUG_CHECK(pad == '0' || pad == ' ');
-  DEBUG_CHECK(padding >= 0);
   DEBUG_CHECK(padding <= kSSizeMax);
   DEBUG_CHECK(!(sign && prefix && *prefix));