Move nacl targets to subdirectories.

This clarifies the structure a bit and is the format recommended by GN style.

Adds annotations to the GYP files for the corresponding GN targets. Removes some dead code in extensions/shell.

[email protected]
[email protected] (chrome/linux/installer)

Reland of https://codereview.chromium.org/1523503002

Review URL: https://codereview.chromium.org/1530663002

Cr-Commit-Position: refs/heads/master@{#365406}
diff --git a/testing/buildbot/gn_isolate_map.pyl b/testing/buildbot/gn_isolate_map.pyl
index 0937535..d20c9a78 100644
--- a/testing/buildbot/gn_isolate_map.pyl
+++ b/testing/buildbot/gn_isolate_map.pyl
@@ -317,7 +317,7 @@
     "type": "unknown",
   },
   "nacl_loader_unittests": {
-    "label": "//components/nacl:nacl_loader_unittests",
+    "label": "//components/nacl/loader:nacl_loader_unittests",
     "type": "raw",
     "args": [],
   },