Get rid of useless calls to AtomicString::impl()

Get rid of useless calls to AtomicString::impl() in the code. This
avoids uselessly calling AtomicString(StringImpl*) constructor
in several cases.

R=abarth
BUG=323739

Review URL: https://codereview.chromium.org/90363003

git-svn-id: svn://svn.chromium.org/blink/trunk@162750 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make HTMLImportLoader a non-RefCounted.

The HTMLImportLoader is owned by HTMLImportsController and
other classes shouldn't have to worry about its life time.
This chang clarifies the intention by making the class non-RefCounted.

R=haraken, dominicc
BUG=none

Review URL: https://codereview.chromium.org/90583003

git-svn-id: svn://svn.chromium.org/blink/trunk@162751 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make LinkResource not a subclass of RefCounted.

LinkResource isn't shared by multiple owners thus doesn't
need to be RefCounted.

R=haraken, dominicc
BUG=none
TEST=none

Review URL: https://codereview.chromium.org/90723002

git-svn-id: svn://svn.chromium.org/blink/trunk@162752 bbb929c8-8fbe-4397-9dbb-9b2b20218538