Avoid double attribute lookup in HTMLElement::matchesReadWritePseudoClass()

Avoid double attribute lookup in HTMLElement::matchesReadWritePseudoClass().
Instead of calling fastHasAttribute() then fastGetAttribute(), call
fastGetAttribute() directly and check if the returned value is nullAtom.

fastHasAttribute() and fastGetAttribute() do exactly the same thing internally
and the only difference is the return type. The attribute lookup is a linear
search and thus it is a good idea to avoid doing it twice.

R=adamk, eseidel

Review URL: https://codereview.chromium.org/184613003

git-svn-id: svn://svn.chromium.org/blink/trunk@168318 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rebaseline virtual/softwarecompositing/fixed-body-background-positioned-expected.txt

For linux only.

TBR=vollick@chromium.org
BUG=

Review URL: https://codereview.chromium.org/185693005

git-svn-id: svn://svn.chromium.org/blink/trunk@168319 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert "Auto-rebaseline for r168303"

This reverts commit e0f8e760cad9f8a63e86bdf451620b5460e4b59c.

Fix tests. Followup to https://codereview.chromium.org/183763024

BUG=
TBR=dongseong.hwang@intel.com

Review URL: https://codereview.chromium.org/185773008

git-svn-id: svn://svn.chromium.org/blink/trunk@168320 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Verify MediaKeys parameter values consistently

Change to use same logic for verifying keySystem and contentType values when creating MediaKeys and MediaKeySessions as is used for isTypeSupported(). Removes unfinished stub code in ContentDecryptionModule.

BUG=342107
TEST=manual

Review URL: https://codereview.chromium.org/183943003

git-svn-id: svn://svn.chromium.org/blink/trunk@168321 bbb929c8-8fbe-4397-9dbb-9b2b20218538