Add some tests for replying to a message

The new tests excercise:
   1) Replying to a message and ensuring the the "fromAccount"
      is the same as is specified in the original message
   2) Handling a "mailto:" url and ensuring that if the account is
      specified in the intent, the "fromAccount" is set to that account

Change the MockProvider so all accounts are correctly
populated

Change test methods to use runTestOnUiThread instead of
Activity#runOnUiThread, as asserts stop the test suite

The new test methods setup the activity in a way that the user
does.  The original test cases should be updated accordingly

Bug: 9823857

Change-Id: I8598fd1b27c57cf8bcd371be8960267a5ac1a770
3 files changed