Require through an internal presubmit that .h|.cc|.inc files contain

either the string ABSL_NAMESPACE_BEGIN or SKIP_ABSL_INLINE_NAMESPACE_CHECK

A lot of files are currently missing one or the other. These will be
updated when the files change (triggering the presubmit on the file)
or though a followup mass update.

PiperOrigin-RevId: 688985640
Change-Id: If2d3f3fcd6b41a7452198ba9de13c8633d6051c6

absl/base/attributes.h

@@ -31,6 +31,8 @@
 // `__has_attribute()` first. If the check fails, we check if we are on GCC and
 // assume the attribute exists on GCC (which is verified on GCC 4.7).
 
+// SKIP_ABSL_INLINE_NAMESPACE_CHECK
+
 #ifndef ABSL_BASE_ATTRIBUTES_H_
 #define ABSL_BASE_ATTRIBUTES_H_
 

absl/base/policy_checks.h

@@ -21,6 +21,8 @@
 // reported with `#error`. This enforcement is best effort, so successfully
 // compiling this header does not guarantee a supported configuration.
 
+// SKIP_ABSL_INLINE_NAMESPACE_CHECK
+
 #ifndef ABSL_BASE_POLICY_CHECKS_H_
 #define ABSL_BASE_POLICY_CHECKS_H_