[Tizen] Fix coding style error
[Tizen] Change MouseDown method

Mouse down event in Elementary Plug don't send it's coordinates, it gets
from the last mouse move. We changed the MouseDown method to trigger the
MouseMove method before.

The dropdown in TizenSystemIndicator landscape mode needs the
last coordinates to succeed.
Merge pull request #1403 from ricardotk/indicator

[Tizen] Change MouseDown method
[Runtime] Move ApplicationSystem to XWalkRunner

ApplicationSystem was being created in RuntimeContext, we now create it
in XWalkRunner.

I've also removed RuntimeContext::GetActiveApplication(), and changed
the callers to use XWalkRunner::GetInstance()->app_system() for
now. While it's usually OK for the tests continue to rely on
XWalkRunner, other uses should be removed in future steps.

I'm targetting first moving the construction to the right place, then
making sure dependencies are passed correctly and we avoid reaching the
global.

Note there's a circular dependency between RuntimeContext and
ApplicationSystem. The current plan is to provide a hook for adding
protocol handlers so that ApplicationSystem (or XWalkRunner) can use it
without RuntimeContext needing to be aware. I'm postponing this change
until there's more knowledge of these relationships.