Insert sampling tracing event macros to DOM constructors

No regression in PerformanceTests/Bindings/create-wrapper.html, which will
be most affected by this CL. This is because the call paths of constructors
are already heavy.

BUG=241743
R=abarth

Review URL: https://chromiumcodereview.appspot.com/18034015

git-svn-id: svn://svn.chromium.org/blink/trunk@153336 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Network Panel: add columns for common response headers.

EOM

BUG=129637

Review URL: https://chromiumcodereview.appspot.com/15735025

git-svn-id: svn://svn.chromium.org/blink/trunk@153337 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Bindings: Use v8::Null instead of caching a null Persistent.

This is needed so that we can get rid of ScopedPersistent::get, and it's sane
anyway.

BUG=236290

Review URL: https://chromiumcodereview.appspot.com/17578008

git-svn-id: svn://svn.chromium.org/blink/trunk@153338 bbb929c8-8fbe-4397-9dbb-9b2b20218538