Defending from failing APIs

Defending from failing APIs.

Some chrome.* API calls may legitimately fail.
Also, chrome.runtime.onInstalled/onStartup callbacks may not happen due to implementation bugs.

We need to rewrite the extension to degrade as little as possible in such cases. In practice, this only means initializing values retrieved from chrome.storage. Since we initialize them upon retrieval, there is no need to initialize them from installed/startup callbacks, so I'm removing them from there.
The only remaining initialization if for activeNotifications; it will be take care of when I start using notifications.getAll API call.

BUG=164227
TEST=Existing tests should work

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=201921

[rgustafson, 2013-05-22 22:04:43]

lgtm

Just leaving a note addressing the concern we talked about:
If storage.get fails, the callback will still be called. If the storage.set
within that callback succeeds, useful information could be overwritten. This
will be fixed later.

[vadimt, 2013-05-22 22:15:15]

On 2013/05/22 22:04:43, rgustafson wrote:
> lgtm
> 
> Just leaving a note addressing the concern we talked about:
> If storage.get fails, the callback will still be called. If the storage.set
> within that callback succeeds, useful information could be overwritten. This
> will be fixed later.

Ack

[skare_, 2013-05-23 00:21:45]

lgtm

[vadimt, 2013-05-23 00:25:09]

estade@, please provide OWNERs approval

[Evan Stade, 2013-05-23 00:54:18]

rslgtm

[commit-bot: I haz the power, 2013-05-23 17:40:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/vadimt@chromium.org/15495008/1

[commit-bot: I haz the power, 2013-05-23 23:16:15]

Change committed as 201921

[not at google - send to devlin, 2013-05-24 00:01:12]

https://chromiumcodereview.appspot.com/15495008/diff/1/chrome/browser/resourc...
File chrome/browser/resources/google_now/background.js (right):

https://chromiumcodereview.appspot.com/15495008/diff/1/chrome/browser/resourc...
chrome/browser/resources/google_now/background.js:246:
storage.get(['activeNotifications', 'recentDismissals'], function(items) {
instead you could call

storage.get({
  'activeNotifications': {},
  'recentDismissals': {}
}, function(items) {
  ...
});

which does the default value handling for you.

[vadimt, 2013-08-21 01:55:43]

On 2013/05/24 00:01:12, kalman wrote:
>
https://chromiumcodereview.appspot.com/15495008/diff/1/chrome/browser/resourc...
> File chrome/browser/resources/google_now/background.js (right):
> 
>
https://chromiumcodereview.appspot.com/15495008/diff/1/chrome/browser/resourc...
> chrome/browser/resources/google_now/background.js:246:
> storage.get(['activeNotifications', 'recentDismissals'], function(items) {
> instead you could call
> 
> storage.get({
>   'activeNotifications': {},
>   'recentDismissals': {}
> }, function(items) {
>   ...
> });
> 
> which does the default value handling for you.

Will this default value mechanism work in case of errors? Like, the database is
corrupted or unavailable: will I get default values (and no error in lastError)?