Mention how to convert "copies" from gyp to gn in the cookbook.

tools/gn/docs/cookbook.md

 # GYP->GN Conversion Cookbook
 
 [TOC]
 
 ## Targets
 
 | *GYP*                                            | *GN*                                               |
 |:-------------------------------------------------|:---------------------------------------------------|
 | `'type': 'static_library', 'name': 'foo',`       | `static_library("foo") {` or `source_set("foo") {` |
 | `'type': 'shared_library', 'name': 'foo',`       | `shared_library("foo") {`                          |
@@ skipping 46 matching lines @@
 Unlike GYP, where an action is a part of a target, GN actions are
 separate targets that you then depend on via deps from other targets:
 
 ```
 action("foo") {
   script = "bar.py"
   outputs = [ "$target_gen_dir/bar.out" ]
   args = [ "--la_dee_da" ]
 }
 
-executable('foo.exe') {
+executable("foo.exe") {
   ...
   deps = [ ":foo" ]  # Depend on the action to make sure it runs.
 }
 ```
 
 Rules in GYP become `action_foreach` in GN which work like actions but
 iterate over a set of sources.
 
+### Copies
+
+GYP
+
+```
+'copies': [
+  {
+    'destination': '<(PRODUCT_DIR)/',
+    'files': [
+      '../build/win/dbghelp_xp/dbghelp.dll',
+    ],
+  },
+],
+```
+
+Unlike GYP, where copies are part of a target, GN copies are
+separate targets that you then depend on via deps from other targets:
+
+```
+copy("bar") {
+  sources = [ "../path/to/secret.dll" ]
+  outputs = [ "$root_out_dir/{{source_file_part}}" ]
+}
+
+component("base") {
+  ...
+  deps = [ "bar" }  # Depend on the copy to make sure it runs.
+}
+```
+
 ## Platform checking
 
 | *GYP*                                | *GN*                 |
 |:-------------------------------------|:---------------------|
 | `'conditions': [['OS=="win"', {`     | `if (is_win) {`      |
 | `'conditions': [['OS=="linux"', {`   | `if (is_linux) {`    |
 | `'conditions': [['OS=="android"', {` | `if (is_android) {`  |
 | `'conditions': [['OS=="mac"', {`     | `if (is_mac) {`      |
 | `'conditions': [['OS=="ios"', {`     | `if (is_ios) {`      |
 | `'conditions': [['chromeos==1', {`   | `if (is_chromeos) {` |
@@ skipping 554 matching lines @@
 
 ```
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("mojo_bindings") {
   sources = [
     "foo.mojom",
   ]
 }
 ```