Update README.md and HACKING.md and resulting yak shave.

sky/HACKING.md

 Hacking on Sky
 ==============
 
 Building
 --------
 
 * Follow the setup & build instructions for [Mojo](https://github.com/domokit/mojo)
 
+The build directory will be `out/Debug` for Linux debug builds, and
+`out/Release` for Linux release builds. For Android builds, prefix
+`android_`, as in, `android_Debug`.
+
 Running applications
 --------------------
 
-* ``./mojo/tools/mojodb start out/Debug [url]``
+To run an application on your device, run:
 
-    `mojodb` has numerous commands, visible via `mojodb help`.  Common ones include:
-    * `mojodb start` BUILD_DIR [url]
-    * `mojodb load` [url]
-    * `mojodb stop`
-    * `mojodb start_tracing` # Starts recoding a performance trace (use stop_tracing to stop)
-    * `mojodb print_crash` # Symbolicate the most recent crash from android.
+* ``./mojo/tools/mojodb start out/android_Debug [url]``
+
+`mojodb` has numerous commands, visible via `mojodb help`.  Common ones include:
+* `mojodb start` BUILD_DIR [url]
+* `mojodb load` [url]
+* `mojodb stop`
+* `mojodb start_tracing` # Starts recoding a performance trace (use stop_tracing to stop)
+* `mojodb print_crash` # Symbolicate the most recent crash from android.
 
 Once `mojodb start` is issued, all subsequent commands will be sent to
 the running mojo_shell instance (even on an attached android device).
 `mojodb start` reads gn args from the passed build directory to
 determine whether its using android, for example.
 
+Running tests
+-------------
+
+Tests are only supported on Linux currently.
+
 * ``./sky/tools/test_sky --debug``
   * This runs the tests against ``//out/Debug``. If you want to run against
     ``//out/Release``, omit the ``--debug`` flag.
 
 Running tests manually
 ----------------------
 
-* ``sky/tools/skygo/linux64/sky_server -t Debug . 8000``
-* ``out/Debug/mojo_shell --args-for="mojo:native_viewport_service --use-headless-config --use-osmesa" --args-for"=mojo:sky_viewer --testing" --content-handlers=text/sky,mojo:sky_viewer --url-mappings=mojo:window_manager=mojo:sky_tester,mojo:surfaces_service=mojo:fake_surfaces_service mojo:window_manager``
+Running tests manually lets you more quickly iterate during
+development; rather than having to compile and rerun all the tests,
+then trawl through the build output to find the current results, you
+can just run the test you're working on and reload it over and over,
+seeing the output right there on your console.
+
+* ``sky/tools/skygo/linux64/sky_server -v -p 8000 out/Debug out/Debug/gen/dart-pkg/packages``
+* ``out/Debug/mojo_shell --args-for="mojo:native_viewport_service --use-headless-config --use-osmesa" --args-for"=mojo:sky_viewer --testing" --content-handlers=application/dart,mojo:sky_viewer --url-mappings=mojo:window_manager=mojo:sky_tester,mojo:surfaces_service=mojo:fake_surfaces_service mojo:window_manager``
 * The ``sky_tester`` should print ``#READY`` when ready
-* Type the URL you wish to run, for example ``http://127.0.0.1:8000/sky/tests/lowlevel/text.html``, and press the enter key
+* Type the URL you wish to run, for example ``http://127.0.0.1:8000/sky/tests/widgets/dialog.dart``, and press the enter key
 * The harness should print the results of the test.  You can then type another URL.
 
 Writing tests
 -------------
 
-* We recommend using the ``unittest.dart`` testing framework.
-* See ``sky/tests/lowlevel/attribute-collection.sky`` for an example.
-
-Adding pixel tests
-------------------
-
-Sky does not have proper pixel tests. Instead we have only reftests.
-If you want a pixel test, you need to dump the png from a reftest,
-upload it to googlestorage and then put and <img> pointing to the
-uploaded file in the reference.
-
-1. Create your test (e.g. foo.sky).
-2. Create an dummy reference file (foo-expected.sky).
-3. Run the test (it will fail).
-4. Copy the -actual.png file to googlestorage (see below).
-5. Put an ``<img>`` pointing to your newly uploaded png in the reference file at
-http://storage.googleapis.com/mojo/sky-pngs/SHA1_HASH_HERE
-
-Copying the file to googlestorage:
-```bash
-$ sha1sum ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
-db0508cdfe69e996a93464050dc383f6480f1283  ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
-$ gsutil.py cp ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png gs://mojo/sky-pngs/db0508cdfe69e996a93464050dc383f6480f1283
-```
-
-Long-term, we should not have these tests at all and should just
-dump paint commands. In the short-term, if we find we're doing this
-a lot we should obviously automate this process, e.g. test_sky could
-do all of this work, including spitting out the correct reference file.
+We recommend using the [Dart
+``test``](https://pub.dartlang.org/packages/test) testing framework.
+See [``sky/tests/raw/color_bounds.dart``](tests/raw/color_bounds.dart)
+for an example.