IDB: Make readonly transactions wait for earlier readwrite transactions

IDB: Make readonly transactions wait for earlier readwrite transactions

The spec recently tightened to more explicitly match the
behavior of non-chrome browsers:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=25251

Blink layout tests are waiting over in
https://codereview.chromium.org/745553002/

BUG=432259
Committed: https://crrev.com/07ece1bfe78c8372a7118dc1de6ae90370fc93d3
Cr-Commit-Position: refs/heads/master@{#305152}

[dgrogan, 2014-11-20 09:23:29]

dgrogan@chromium.org changed reviewers:
+ jsbell@chromium.org

[dgrogan, 2014-11-20 09:23:29]

Josh, could you review this? layout test is in
https://codereview.chromium.org/745553002/

[jsbell, 2014-11-20 18:40:18]

LGTM

Can you elaborate a bit more in the CL description, e.g. link to spec bug and to
the CL with the test?

[dgrogan, 2014-11-21 01:30:36]

The CQ bit was checked by dgrogan@chromium.org

[commit-bot: I haz the power, 2014-11-21 01:32:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/742033002/1

[commit-bot: I haz the power, 2014-11-21 03:11:09]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-21 03:11:52]

Patchset 1 (id:??) landed as
https://crrev.com/07ece1bfe78c8372a7118dc1de6ae90370fc93d3
Cr-Commit-Position: refs/heads/master@{#305152}