DevTools: Overriding the String global object and opening the debugger crashes the browser tab and stops the debugger

BUG=305199

Review URL: https://codereview.chromium.org/26640005

git-svn-id: svn://svn.chromium.org/blink/trunk@159259 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add support for [TreatNullAs] extended attribute for reflected attributes

Add support for [TreatNullAs] extended attribute for reflected attributes and fix the
bindings generator so that [Reflect] no longer implies [TreatNullAs=NullString].
This way, newly introduced reflected attributes will behave according to specification.

This CL adds [TreatNullAs=NullString] extended attribute to all existing reflected
attributes of type DOMString so that there is no web-exposed behavior change. This
makes it more explicit that we treat null as the Null string for those attributes and
it makes it clear that we don't match the specifications in many cases.

In follow-up patches, we should gradually remove those [TreatNullAs=NullString]
extended attributes for reflected attributes when the specification does not indicate
[TreatNullAs=EmptyString] and when other browser behave according to the
specification.

R=arv, haraken
BUG=304959

Review URL: https://codereview.chromium.org/26694003

git-svn-id: svn://svn.chromium.org/blink/trunk@159260 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Restore expectation for fast/js/JSON-stringify.html dropped in r159254.

TBR=ojan@chromium.org
BUG=159254

Review URL: https://codereview.chromium.org/26584006

git-svn-id: svn://svn.chromium.org/blink/trunk@159261 bbb929c8-8fbe-4397-9dbb-9b2b20218538