Is dead code elimination really working?

I can't seem to bring the code size down with a barely empty project through dead-code elimination alone, even when following the installation instructions to the letter.

The template used was [reagent-figwheel](https://github.com/gadfly361/reagent-figwheel) with only `devtools` and `reagent` as dependencies. I've fiddled with the `goog.DEBUG` flag, and then removed `devtools` from the `:require` and `:dependencies` vectors.

| Type | Size |
|--------------------------------------------------------|-------:|
| `:dependencies` + `:require` + `goog.DEBUG true` | 1.9 MB |
| `:dependencies` + `:require` + `goog.DEBUG false` | 1.5 MB |
| `:dependencies` + `:require` + no mention at all | 1.6 MB |
| `:dependencies` + no `:require` + no mention at all | 763 KB |
| no `:dependencies` + no `:require` + no mention at all | 763 KB |

The first two rows followed the instructions from the [release notes](https://github.com/binaryage/cljs-devtools/releases/tag/v0.5.3). There's a single mention of ` (devtools/install!)` within a `(when ^boolean js/goog.DEBUG ...)` block. The other three had this line removed manually.

Google Closure's shaved 400kb of the build, but that's still a 800kb increase for a `:require` without a single mention of `devtools`! Is this the best I can expect from dead code elimination?

Here's the code used for the builds (e.g. `lein new reagent-figwheel +devtools`):
```clojure
;##################
;### profile.cljs

(defproject devtools-dce "0.1.0-SNAPSHOT"
:dependencies [[org.clojure/clojure "1.8.0"]
[org.clojure/clojurescript "1.9.229"]
[reagent "0.6.0"]
[binaryage/devtools "0.8.2"]]

[...]

:cljsbuild
{:builds
[{:id "min"
:source-paths ["src/cljs"]
:compiler {:main devtools-dce.core
:optimizations :advanced
:output-to "resources/public/js/compiled/app.js"
:output-dir "resources/public/js/compiled/min"
:closure-defines {goog.DEBUG false}
:pseudo-names true ;; added to exacerbate size difference
:pretty-print false}}

]})

;##############
;## core.cljs

(ns devtools-dce.core
(:require
[reagent.core :as reagent]
[devtools.core :as devtools]
))

[...]

(defn dev-setup [] ;; inlining into `main` made no difference
(when ^boolean js/goog.DEBUG
(enable-console-print!)
(println "dev mode")
(devtools/install!)
))

(defn ^:export main []
(dev-setup)
(reload))
```

Bắt đầu với cấu hình build trong profile.cljs và namespace cùng điểm vào dev-setup trong core.cljs, sử dụng template reagent-figwheel và các thiết lập advanced-optimization được liệt kê. Tái hiện năm build và so sánh kích thước đầu ra của chúng; hoàn thành có nghĩa là giải thích liệu dependency devtools không được sử dụng có bị loại bỏ hay không, đồng thời ghi lại hoặc sửa kết quả quan sát được.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.