Make js2c depend on messages.h

Make js2c depend on messages.h

messages.h defined the constants used for error messages. The js2c
target needs to be rebuilt when messages.h changes.

BUG=N
LOG=N
R=machenbach@chromium.org, yang@chromium.org, domenic@chromium.org

[arv (Not doing code reviews), 2015-06-09 16:16:22]

PTAL

https://codereview.chromium.org/1169853007/diff/1/BUILD.gn
File BUILD.gn (right):

https://codereview.chromium.org/1169853007/diff/1/BUILD.gn#newcode318
BUILD.gn:318: "src/messages.h",
I don't think js2c_extras depends on this but I'm not really sure?

[domenic, 2015-06-09 16:24:56]

https://codereview.chromium.org/1169853007/diff/1/BUILD.gn
File BUILD.gn (right):

https://codereview.chromium.org/1169853007/diff/1/BUILD.gn#newcode318
BUILD.gn:318: "src/messages.h",
On 2015/06/09 at 16:16:22, arv wrote:
> I don't think js2c_extras depends on this but I'm not really sure?

Yeah I checked and it doesn't. BuildFilterChain vs. BuildExtraFilterChain.

[domenic, 2015-06-09 16:25:46]

lgtm

[domenic, 2015-06-09 16:26:53]

On 2015/06/09 at 16:25:46, domenic wrote:
> lgtm

... except the gn build is failing because of newline in string constant. So,
not lgtm I guess. Sorry for spam.

[arv (Not doing code reviews), 2015-06-09 16:32:57]

I don't think this CL is correct. Now that I look at it closer, all these rules
already list src/messages.h through library_files and
experimental_library_files.

[Michael Achenbach, 2015-06-10 10:09:52]

CC vogelheim@chromium.org who works on a fix for some of the missing
dependencies. Looks like make doesn't create the
external snapshot in some cases on linux64 in release mode.

[arv (Not doing code reviews), 2015-06-10 13:55:24]

Closing this since this is not the problem