Refactoring: Move m_mayDisplaySeamlesslyWithParent down to Document

The member is used only in Document, thus no reason to
stay in SecurityContext.

TEST=none
BUG=none
R=haraken@chromium.org, abarth, haraken, hayato

Review URL: https://codereview.chromium.org/27615003

git-svn-id: svn://svn.chromium.org/blink/trunk@159829 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use EventTargetWithInlineData instead of EventTarget

Inherit from EventTargetWithInlinedata rather than EventTarget,
which was introduced at r159393, to reduce redundant overrides.

BUG=none
TEST=pass all tests
R=tkent@chromium.org

Review URL: https://codereview.chromium.org/27634002

git-svn-id: svn://svn.chromium.org/blink/trunk@159830 bbb929c8-8fbe-4397-9dbb-9b2b20218538
FrameView never contains null scrollable areas.

Because that's crazy.

BUG=307486

Review URL: https://codereview.chromium.org/26547004

git-svn-id: svn://svn.chromium.org/blink/trunk@159831 bbb929c8-8fbe-4397-9dbb-9b2b20218538