Make DOMError constructible

Make DOMError constructible as per the DOM4 specification:
http://dom.spec.whatwg.org/#domerror

This matches the behavior of Firefox 28. IE11 exposes DOMError on the global
Window object but it is not constructible.

R=arv@chromium.org, tkent@chromium.org
BUG=367565
TEST=fast/dom/DOMError-constructor.html

Review URL: https://codereview.chromium.org/254823007

git-svn-id: svn://svn.chromium.org/blink/trunk@172718 bbb929c8-8fbe-4397-9dbb-9b2b20218538
ScriptStateToId should be a map from RefPtr<NewScriptState> to int

Currently InjectedScriptManager and InspectorRuntimeAgent hold a map from NewScriptState* to int. However, this is dangerous since no one keeps the NewScriptState* alive. We should use RefPtr<NewScriptState>. (Note: Using RefPtr<NewScriptState> won't cause any cycle because it doesn't hold a strong reference to anything.)

BUG=367069

Review URL: https://codereview.chromium.org/251803002

git-svn-id: svn://svn.chromium.org/blink/trunk@172719 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move ALLOW_UNUSED after identifiers.

This CL makes usage of ALLOW_UNUSED consistent with Chromium.

BUG=

Review URL: https://codereview.chromium.org/256733002

git-svn-id: svn://svn.chromium.org/blink/trunk@172720 bbb929c8-8fbe-4397-9dbb-9b2b20218538