Add a sky media service to make it possible to play a sound.

I didn't exactly follow the android API, but pretty close.

Also started a java/common implementation for things like
DataPipeUtils. I only needed the ability to copy from a data
pipe to a file, so that's the only function we have so far.

Fixes https://github.com/domokit/mojo/issues/270

R=abarth@chromium.org, abarth@google.com

Review URL: https://codereview.chromium.org/1211913005.
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index 54e71f0..7f55975 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -34,6 +34,7 @@
   if (is_android) {
     deps += [
       "//mojo/android",
+      "//mojo/java",
       "//mojo/tools/android_shortcuts",
       "//mojo/tools:remote_file_reader",
     ]