Rename //build/config/linux/nss and fix comments

Historically, we used a combination of bundled OpenSSL/BoringSSL,
bundled NSS, and system NSS on different platforms (including a time
when we bundled part of NSS and sourced the rest from the system). Some
of the comments and target name reflected that. Things are simpler now.
See bug.

In //chromeos, it seems the dependency was not actually needed, so I've
removed it. (NSS is used in parts of //chromeos, but only in
subdirectories. Those seem to be pulling it in via //crypto:platform,
which I've left a TODO to tidy up.)

Bug: 1227773
Change-Id: I089f868f0ac012f7a87d8928a4e3cbd931d9ba9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3309100
Reviewed-by: Matt Mueller <mattm@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Brian Geffon <bgeffon@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/main@{#947206}

build/config/linux/nss/BUILD.gn

@@ -5,14 +5,10 @@
 import("//build/config/linux/pkg_config.gni")
 
 if (is_linux || is_chromeos) {
-  # This is a dependency on NSS with no libssl. On Linux we use a built-in SSL
-  # library but the system NSS libraries. Non-Linux platforms using NSS use the
-  # hermetic one in //third_party/nss.
-  #
-  # Generally you should depend on //crypto:platform instead of using this
-  # config since that will properly pick up NSS or OpenSSL depending on
-  # platform and build config.
-  pkg_config("system_nss_no_ssl_config") {
+  # This is a dependency on NSS with no libssl3. On Linux and Chrome OS, we use
+  # NSS for platform certificate integration. We use our own TLS library, so
+  # exclude the one from NSS.
+  pkg_config("nss") {
     packages = [ "nss" ]
     extra_args = [
       "-v",

chromeos/BUILD.gn

@@ -27,10 +27,7 @@ component("chromeos") {
   sources = []
 
   if (is_chromeos_ash) {
-    configs += [
-      ":chromeos_implementation",
-      "//build/config/linux/nss:system_nss_no_ssl_config",
-    ]
+    configs += [ ":chromeos_implementation" ]
     if (is_chromeos_device) {
       configs += [ "//build/config/compiler:use_orderfile_for_hugepage" ]
     }
@@ -130,10 +127,7 @@ source_set("test_utils") {
 }
 
 test("chromeos_unittests") {
-  configs += [
-    "//build/config/linux/dbus",
-    "//build/config/linux/nss:system_nss_no_ssl_config",
-  ]
+  configs += [ "//build/config/linux/dbus" ]
 
   deps = [
     "//base/test:test_support",

chromeos/memory/BUILD.gn

@@ -14,10 +14,7 @@ config("chromeos_implementation") {
 
 component("memory") {
   defines = [ "IS_CHROMEOS_MEMORY_IMPL" ]
-  configs += [
-    ":chromeos_implementation",
-    "//build/config/linux/nss:system_nss_no_ssl_config",
-  ]
+  configs += [ ":chromeos_implementation" ]
   deps = [
     "//base",
     "//chromeos:chromeos_export",
@@ -45,7 +42,6 @@ component("memory") {
 
 source_set("unit_tests") {
   testonly = true
-  configs += [ "//build/config/linux/nss:system_nss_no_ssl_config" ]
   deps = [
     ":memory",
     "//base/test:test_support",

chromeos/memory/userspace_swap/BUILD.gn

@@ -23,10 +23,7 @@ mojom("mojom") {
 }
 
 component("userspace_swap") {
-  configs += [
-    ":chromeos_implementation",
-    "//build/config/linux/nss:system_nss_no_ssl_config",
-  ]
+  configs += [ ":chromeos_implementation" ]
   deps = [
     ":mojom",
     "//base",
@@ -56,7 +53,6 @@ component("userspace_swap") {
 
 source_set("unit_tests") {
   testonly = true
-  configs += [ "//build/config/linux/nss:system_nss_no_ssl_config" ]
   deps = [
     ":mojom",
     ":userspace_swap",

crypto/BUILD.gn

@@ -203,15 +203,19 @@ static_library("test_support") {
   ]
 }
 
-# This is a meta-target that forwards to NSS's SSL library or OpenSSL,
-# according to the state of the crypto flags. A target just wanting to depend
-# on the current SSL library should just depend on this.
+# This target historically abstracted between different cryptography and TLS
+# libraries. Now we always use //third_party/boringssl for cryptography and TLS.
+# On Linux and Chrome OS, we additionally use //build/config/linux/nss for some
+# certificate-related platform integration points. Depend on one or both of the
+# individual targets instead of this one.
+#
+# TODO(https://crbug.com/1275165): Remove this target.
 group("platform") {
   public_deps = [ "//third_party/boringssl" ]
 
   # Link in NSS if it is used for the platform certificate library
   # (use_nss_certs).
   if (use_nss_certs) {
-    public_configs = [ "//build/config/linux/nss:system_nss_no_ssl_config" ]
+    public_configs = [ "//build/config/linux/nss" ]
   }
 }