Fix a command in android build doc

docs/android_build_instructions.md

 # Checking out and building Chromium for Android
 
 There are instructions for other platforms linked from the
 [get the code](get_the_code.md) page.
 
 ## Instructions for Google Employees
 
 Are you a Google employee? See
 [go/building-chrome](https://goto.google.com/building-chrome) instead.
 
@@ skipping 116 matching lines @@
 
 ## Setting up the build
 
 Chromium uses [Ninja](https://ninja-build.org) as its main build tool along
 with a tool called [GN](../tools/gn/docs/quick_start.md) to generate `.ninja`
 files. You can create any number of *build directories* with different
 configurations. To create a build directory which builds Chrome for Android,
 run:
 
 ```shell
-$ gn gen '--args="target_os="android"' out/Default
+$ gn gen --args='target_os="android"' out/Default
 ```
 
 * You only have to run this once for each new build directory, Ninja will
   update the build files as needed.
 * You can replace `Default` with another name, but
   it should be a subdirectory of `out`.
 * For other build arguments, including release settings, see [GN build
   configuration](https://www.chromium.org/developers/gn-build-configuration).
   The default will be a debug component build matching the current host
   operating system and CPU.
@@ skipping 228 matching lines @@
 release of Chrome for Android (v25+) you can do the following steps.
 Note that in order to get your changes into the official release, you'll
 need to send your change for a codereview using the regular process for
 committing code to chromium.
 
 1.  Open Chrome on your Android device and visit chrome://version
 2.  Copy down the id listed next to "Build ID:"
 3.  Go to
     [http://storage.googleapis.com/chrome-browser-components/BUILD\_ID\_FROM\_STEP\_2/index.html](http://storage.googleapis.com/chrome-browser-components/BUILD_ID_FROM_STEP_2/index.html)
 4.  Download the listed files and follow the steps in the README.