Improve robustness of pageCapture.saveAsMHTML custom binding

Improve robustness of pageCapture.saveAsMHTML custom binding

Previously, errors in the user-defined callback function could break the
internal state of the pageCapture API. This is now mitigated by reading
and nulling the callback before using it, and only access the properties
of the response object after verifying that it is not void.

Also fixed a typo in an error message.

BUG=392800
TEST=Manually the tests from the bug report (or read the source code and
infer from the changes that the reported bugs have been fixed.)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282470

[Devlin, 2014-07-10 20:53:28]

Good find!

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
File chrome/renderer/resources/extensions/page_capture_custom_bindings.js
(right):

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
chrome/renderer/resources/extensions/page_capture_custom_bindings.js:20: if
(response) {
nit: inline?

if (response)
  response = CreateBlob(response.mthmlFilePath, response.mhtmlFileLength);

or even

response = response ?
    CreateBlob(response.mthmlFilePath, response.mhtmlFileLength) :
    undefined;

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
chrome/renderer/resources/extensions/page_capture_custom_bindings.js:28: }
finally {
We usually put a catch here and log the error so the developer can see what went
wrong, e.g.:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/renderer/re...

[robwu, 2014-07-10 21:15:56]

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
File chrome/renderer/resources/extensions/page_capture_custom_bindings.js
(right):

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
chrome/renderer/resources/extensions/page_capture_custom_bindings.js:20: if
(response) {
On 2014/07/10 20:53:28, Devlin wrote:
> nit: inline?
> 
> if (response)
>   response = CreateBlob(response.mthmlFilePath, response.mhtmlFileLength);
> 
> or even
> 
> response = response ?
>     CreateBlob(response.mthmlFilePath, response.mhtmlFileLength) :
>     undefined;

Done.

https://codereview.chromium.org/384653002/diff/20001/chrome/renderer/resource...
chrome/renderer/resources/extensions/page_capture_custom_bindings.js:28: }
finally {
On 2014/07/10 20:53:28, Devlin wrote:
> We usually put a catch here and log the error so the developer can see what
went
> wrong, e.g.:
>
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/renderer/re...

Done.

[Devlin, 2014-07-10 21:20:09]

lgtm

[robwu, 2014-07-10 21:20:36]

The CQ bit was checked by rob@robwu.nl

[commit-bot: I haz the power, 2014-07-10 21:22:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rob@robwu.nl/384653002/40001

[commit-bot: I haz the power, 2014-07-10 23:43:23]

Change committed as 282470