Revert of purge nss files and dependencies

webrtc/base/BUILD.gn

Index: webrtc/base/BUILD.gn
diff --git a/webrtc/base/BUILD.gn b/webrtc/base/BUILD.gn
index be41cad5c9be3e6f2dc779c2fdbd31bf22f2b4f9..475252c3ff975780a45a5671085020af00315a07 100644
--- a/webrtc/base/BUILD.gn
+++ b/webrtc/base/BUILD.gn
@@ -39,6 +39,14 @@
   ]
 }
 
+config("nss_config") {
+  defines = [
+    "SSL_USE_NSS",
+    "HAVE_NSS_SSL_H",
+    "SSL_USE_NSS_RNG",
+  ]
+}
+
 config("ios_config") {
   libs = [
     "CFNetwork.framework",
@@ -75,6 +83,15 @@
     if (use_openssl) {
       deps = [
         "//third_party/boringssl",
+      ]
+    } else {
+      deps = [
+        "//net/third_party/nss/ssl:libssl",
+      ]
+
+      public_configs = [
+        "//net/third_party/nss/ssl:ssl_config",
+        "//third_party/nss:system_nss_no_ssl_config",
       ]
     }
   }
@@ -480,6 +497,31 @@
       "opensslstreamadapter.cc",
       "opensslstreamadapter.h",
     ]
+  } else {
+    public_configs += [ ":nss_config" ]
+    if (rtc_build_ssl) {
+      if (build_with_chromium) {
+        deps += [ "//crypto:platform" ]
+      } else {
+        deps += [ "//net/third_party/nss/ssl:libssl" ]
+        if (is_linux) {
+          deps += [ ":linux_system_ssl" ]
+        } else {
+          deps += [
+            "//third_party/nss:nspr",
+            "//third_party/nss:nss",
+          ]
+        }
+      }
+    } else {
+      configs += [ "external_ssl_library" ]
+    }
+    sources += [
+      "nssidentity.cc",
+      "nssidentity.h",
+      "nssstreamadapter.cc",
+      "nssstreamadapter.h",
+    ]
   }
 
   if (is_android) {