gdata: Make WeakPtrFactory the last parameter

gdata: Make WeakPtrFactory the last parameter

Remove WeakPtr members in favor of WeakPtrFactory::GetWeakPtr()
Along the way, copy derat's comment from ContactDatabase on this matter.

Wez on [chromium-dev] Weak ptrs for derived types?

You need to be similarly careful to have WeakPtrFactory appear after any
fields that its WeakPtrs may be used to access if you follow that pattern
instead.

BUG=none
TEST=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=149576

[Daniel Erat, 2012-08-01 23:06:13]

lgtm

[commit-bot: I haz the power, 2012-08-02 00:11:39]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/satorux@chromium.org/10837061/1

[commit-bot: I haz the power, 2012-08-02 00:49:06]

Try job failure for 10837061-1 (retry) on linux_chromeos for step "compile"
(clobber build).
It's a second try, previously, step "compile" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_chro...