Make built-ins strict mode conforming, and support a --use-strict flag.

Make built-ins strict mode conforming, and support a --use-strict flag.

* Turned all uses of 'const' into 'var'.
* Turned all uses of local 'function' into 'var'.
* Added a couple of missing toplevel 'var' declarations.

One consequence is that the properties on the builtin object  are no longer
non-writable, and I had to adapt one test. Is that a problem?

Unfortunately, we cannot actually switch the library scripts to strict mode
by default, because that makes observable things like poisoned .caller properties
for library functions.

Also removed dead flag code in Compiler::Compile.

R=yangguo@chromium.org
BUG=
TEST=

Committed: https://code.google.com/p/v8/source/detail?r=10758

[Yang, 2012-02-17 08:22:55]

LGTM with comments.

https://chromiumcodereview.appspot.com/9415010/diff/1/src/collection.js
File src/collection.js (right):

https://chromiumcodereview.appspot.com/9415010/diff/1/src/collection.js#newco...
src/collection.js:28: "use strict";
Some of the .js files have "use strict", some don't. Intentional?

https://chromiumcodereview.appspot.com/9415010/diff/1/src/mirror-debugger.js
File src/mirror-debugger.js (right):

https://chromiumcodereview.appspot.com/9415010/diff/1/src/mirror-debugger.js#...
src/mirror-debugger.js:27: 
Why new empty line?

[rossberg, 2012-02-17 09:20:17]

I'll wait a bit longer with landing this, in case anybody has concerns regarding
making the builtin object mutable.

http://codereview.chromium.org/9415010/diff/1/src/collection.js
File src/collection.js (right):

http://codereview.chromium.org/9415010/diff/1/src/collection.js#newcode28
src/collection.js:28: "use strict";
On 2012/02/17 08:22:55, Yang wrote:
> Some of the .js files have "use strict", some don't. Intentional?

Yes. I spent the better part of my evening trying to get in "use strict"
everywhere, but lots of things went wrong: some tests failed that traverse the
.caller chain through higher-order library functions in array and string; the
debugger started executing all tests in strict mode (and thus failing), for
reasons that I didn't understand at all; and worst, with v8natives and runtime,
I even had weird crashes and assertion failures -- apparently, some of the
low-level code and primitive rely on sloppy semantics.

In the end, I just gave up and decided to keep everything sloppy by default,
except for new Harmony libs, and auxiliaries like message.js.

Long-term goal should be to get rid of it, but I leave that for future work.

http://codereview.chromium.org/9415010/diff/1/src/mirror-debugger.js
File src/mirror-debugger.js (right):

http://codereview.chromium.org/9415010/diff/1/src/mirror-debugger.js#newcode27
src/mirror-debugger.js:27: 
On 2012/02/17 08:22:55, Yang wrote:
> Why new empty line?

Because I had a "use strict" in here at some point that I reverted imperfectly.
;)

Done.