Refactor PendingScript / HTMLScriptRunner.

Refactor PendingScript / HTMLScriptRunner.

Goal: PendingScript should know how to watch for its resource to load, and upper
layers (such as HTMLScriptRunner) should delegate the "how to watch for load"
logic to PendingScript, instead of accessing its resource directly.

In addition, a function to extract source code from PendingScript should be in
PendingScript, not in HTMLScriptRunner.

The refactoring is split off from https://codereview.chromium.org/368283002
(script streaming), but it makes sense as standalone too.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181627

[marja, 2014-09-09 07:44:29]

marja@chromium.org changed reviewers:
+ haraken@chromium.org

[marja, 2014-09-09 07:44:29]

haraken, ptal.

I think this refactoring would make sense as a standalone; wdyt?

[haraken, 2014-09-09 07:50:48]

LGTM

[marja, 2014-09-09 08:04:48]

The CQ bit was checked by marja@chromium.org

[commit-bot: I haz the power, 2014-09-09 08:05:10]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/marja@chromium.org/551293002/1

[commit-bot: I haz the power, 2014-09-09 09:24:45]

Committed patchset #1 (id:1) as 181627