Update AssertMatchingEnums.cpp now that everything is in blink namespace

Update AssertMatchingEnums.cpp now that everything is in blink namespace.
This CL defines all assertions inside the blink namespace as well so that we
don't have have to specify blink:: explicitly in the assertion macro. Public
names cannot be identical to core blink ones anyway or they would clash now
that they are in the same namespace.

As a side effect, the same COMPILE_ASSERT_MATCHING_*() macros could now be
reused for enumerations that are not in the blink namespace (e.g. in the WTF
one) since the macros no longer specify blink:: explicitly.

This CL also removes a few outdated references to WebKit / WebCore.

R=abarth@chromium.org, eseidel@chromium.org

Review URL: https://codereview.chromium.org/416313006

git-svn-id: svn://svn.chromium.org/blink/trunk@179160 bbb929c8-8fbe-4397-9dbb-9b2b20218538