Introduce ASSERT_ENABLED macro.

We have ASSERT_DISABLED macro, and it is typically used as

#if !ASSERT_DISABLED
...
#endif

Double negative is not good for readability. We can write it with ASSERT_ENABLED
as following:

#if ASSERT_ENABLED
...
#endif

TEST=none; no behavior changes
BUG=

Review URL: https://codereview.chromium.org/216313002

git-svn-id: svn://svn.chromium.org/blink/trunk@170280 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r170250

http://src.chromium.org/viewvc/blink?view=revision&revision=170250

TBR=vollick@chromium.org

Review URL: https://codereview.chromium.org/216483002

git-svn-id: svn://svn.chromium.org/blink/trunk@170281 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Persist network panel resource type filter.

+minor refactoring.

BUG=354131

Review URL: https://codereview.chromium.org/212933011

git-svn-id: svn://svn.chromium.org/blink/trunk@170282 bbb929c8-8fbe-4397-9dbb-9b2b20218538