Introduce dartanalyze into our build.

README.md

 Mojo
 ====
 
 Mojo is an effort to extract a common platform out of Chrome's renderer and plugin processes that can support multiple types of sandboxed content, such as HTML, Pepper, or NaCl.
 
 ## Set up your environment
 
 The instructions below only need to be done once. Note that a simple "git clone" command is not sufficient to build the source code because this repo uses the gclient command from depot_tools to manage most third party dependencies.
 
 1. Download depot_tools and make sure it is in your path:<br>http://www.chromium.org/developers/how-tos/install-depot-tools<br>
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 Finally, perform the build. The result will be in out/android_Debug:
 
 ```
 $ mojo/tools/mojob.py build --android
 ```
 
 If you see javac compile errors, make sure you have an up-to-date JDK:
 https://code.google.com/p/chromium/wiki/AndroidBuildInstructions#Install_Java_JDK
 
+## Dart Code
+
+Because the dart analyzer is a bit slow, we don't run it unless the user specifically asks for it. To run the dart analyzer against the list of dart targets in the toplevel BUILD.gn file, run:
+
+```
+$ mojo/tools/mojob.py dartcheck
+```
+
 ## Googlers
 
 If you're a Googler, you can use Goma, a distributed compiler service for open-source projects such as Chrome and Android. The instructions below assume that Goma is installed in the default location (~/goma).
 
 To enable Goma, update your "args.gn" file. Open the file in your editor with this command:
 ```
 $ gn args out/Debug
 ```
 
 Add this line to the end of the file:
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     ```
     ./out/Debug/mojo_shell mojo:sample_app
     ```
 
 3. Optional: Run Mojo Shell with an HTTP server
     ```
     cd out/Debug
     python -m SimpleHTTPServer 4444 &
     ./mojo_shell --origin=http://127.0.0.1:4444 --disable-cache mojo:sample_app
     ```