Drop ScriptState argument from global Cache Storage accessor.

Drop ScriptState argument from global Cache Storage accessor.

We only need an ExecutionContext and that can be obtained from the
global scope that is implicitly passed in. Simplifies the IDL.

R=dmurph@chromium.org
BUG=439389
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=193068

[jsbell, 2015-04-03 00:21:25]

The CQ bit was checked by jsbell@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-04-03 00:22:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051363004/1

[commit-bot: I haz the power, 2015-04-03 00:38:13]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-03 00:38:14]

Try jobs failed on following builders:
  blink_presubmit on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/3...)

[dmurph, 2015-04-03 00:47:20]

lgtm

[jsbell, 2015-04-03 01:12:49]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2015-04-03 01:17:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051363004/1

[commit-bot: I haz the power, 2015-04-03 03:48:52]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=193068