tools/gn: Give a better informative message if user uses apostrophe.

tools/gn: Give a better informative message if user uses apostrophe.

Since most most gn users come from gyp and that apostrophe
works as a string delimiter in both gyp and python, it is pretty common
that they use an apostrophe (') instead of a double one (").

So lets try to give them a more helpful error message that could save people
some time the first time.

BUG=469097
TEST=edit any BUILD.gn and change any " by '. regenerate the ninja files
by running gn gen out-gn. See the error message.
R=brettw@chromium.org

Committed: https://crrev.com/dd495008e9a6652a7147d91fe3bdf52c5325de55
Cr-Commit-Position: refs/heads/master@{#321813}

[tfarina, 2015-03-22 10:50:32]

Brett, is this correct?

[Daniel Bratell, 2015-03-23 09:05:22]

bratell@opera.com changed reviewers:
+ bratell@opera.com

[Daniel Bratell, 2015-03-23 09:05:22]

https://codereview.chromium.org/1024333002/diff/1/tools/gn/tokenizer.cc
File tools/gn/tokenizer.cc (right):

https://codereview.chromium.org/1024333002/diff/1/tools/gn/tokenizer.cc#newco...
tools/gn/tokenizer.cc:392: help = "I expected \" but got ' instead.";
Since this might also be a spurious ' in the middle of nothing, maybe:

"Strings are delimited by \" characters, not apostrophes."

If it was intended as a string, it will be obvious enough. If it was not
intended as a string, it will be obvious that it was about to be parsed as one.

[tfarina, 2015-03-23 10:40:51]

https://codereview.chromium.org/1024333002/diff/1/tools/gn/tokenizer.cc
File tools/gn/tokenizer.cc (right):

https://codereview.chromium.org/1024333002/diff/1/tools/gn/tokenizer.cc#newco...
tools/gn/tokenizer.cc:392: help = "I expected \" but got ' instead.";
On 2015/03/23 09:05:22, Daniel Bratell wrote:
> Since this might also be a spurious ' in the middle of nothing, maybe:
> 
> "Strings are delimited by \" characters, not apostrophes."
> 
> If it was intended as a string, it will be obvious enough. If it was not
> intended as a string, it will be obvious that it was about to be parsed as
one.

Done.

[brettw, 2015-03-23 17:26:08]

lgtm

[tfarina, 2015-03-23 18:29:10]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-03-23 18:29:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1024333002/20001

[commit-bot: I haz the power, 2015-03-23 18:34:35]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-23 18:35:22]

Patchset 2 (id:??) landed as
https://crrev.com/dd495008e9a6652a7147d91fe3bdf52c5325de55
Cr-Commit-Position: refs/heads/master@{#321813}