Simplify CachedResource::data

Simplify CachedResource::data

* Remove allDataReceived parameter from data(), do the end-of-load work in
    finishOnePart(), which is called by finish() and called directly for
    multipart loads.
* Many subclass do work in data() only if allDataReceived is true. Do this
    work in checkNotify() instead.
* Move calling setEncodedSize() into CachedResurce::data() instead of the
    subclasses, as it's duplicated in nearly every subclass.

BUG=none
TEST=none

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=148406

[eseidel, 2013-04-15 23:08:50]

A method named "data" with no return value makes no sense to me. :)  But that's
a patch for another time.

lgtm.

[Nate Chapin, 2013-04-15 23:10:29]

Committed patchset #1 manually as r148406 (presubmit successful).