Changing the zlib BUILD.gn rule for the inflate chunk copy code to use the much less permissive chromium compiler:chromium_code config (diff follows)

 source_set("zlib_inflate_chunk_simd") {
   ...
-  configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
-
   public_configs = [ ":zlib_inflate_chunk_simd_config" ]
 }

produces warnings:

../../third_party/zlib/contrib/optimizations/chunkcopy.h:114:19: error: comparison of integers of different signs: 'long' and 'unsigned long' [-Werror,-Wsign-compare]
  if (limit - out < CHUNKCOPY_CHUNK_SIZE) {
      ~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~

../../third_party/zlib/contrib/optimizations/chunkcopy.h:399:19: error: comparison of integers of different signs: 'long' and 'unsigned long' [-Werror,-Wsign-compare]
  if (limit - out < CHUNKCOPY_CHUNK_SIZE * 3) {

Since zlib is compiled in C, correct, these are errors.  

The left side of the expression is ptrdiff_t type, and the right side of the expression should be ptrdiff_t also.  But it is size_t.

We should fix the comparison, and use compiler:chromium_code more to prevent similar errors slipping into the code in future.