Mojo: Make tests under mojo/public use our own run_all_unittests.cc.

Split off run_all_unittests.cc to its own static library and make the
various test targets under mojo/public depend on that. This way they
don't have to call CoreImpl::Init() themselves.

Also temporarily disable public/bindings/sample/sample_test.cc until I
convert it to a gtest, which I'll do separately.

R=sky@chromium.org, sky

Review URL: https://codereview.chromium.org/68203005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234280 0039d316-1c4b-4281-b951-d872f2087c98
Reenabling ImeTests.

Changing the page scale factor to non 1 value.
Tests passed 20 runs locally.

NOTRY=true
BUG=315548

Review URL: https://codereview.chromium.org/69243002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234281 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234281