Fix long-press image selection inside editables.
This fixes the regression introduced in http://crrev.com/1668453002 that
contenteditable images were no longer selectable with long-press, and
also fixes the longer-standing issue that long-press selection only worked
on the left side of images.
I also removed unnecessary #if OS(ANDROID), which allows the long-press behavior
to work similarly on other touch platforms and lets us run the tests on
all platforms.
BUG=597506, 585020
Review URL: https://codereview.chromium.org/1845193002
Cr-Commit-Position: refs/heads/master@{#385360}
4 files changed
