ApplicationFileUtil: Stop leaking |prev_value|.

Stop allocating memory for a base::DictionaryValue() that is immediately
going to be overwritten, as the initial value then leaks.

CID=194508
CID=194777
BUG=XWALK-2928

(cherry picked from commit fac3b4f24ab7848d343a45bcbcd253c26f31ef4a)
[Android] Remove XWalkRenderViewExt::capture_picture_enabled_.

This variable was never used anywhere ever since it was introduced, and
was not being initialized in the constructor.

CID=194717
BUG=XWALK-2928

(cherry picked from commit a0393e834ba61837b51fa29502fa47ef450b8329)

Conflicts:
	runtime/renderer/android/xwalk_render_view_ext.h
[SysApps] raw_socket: Initialize |write_buffer_size_|.

The member variable was not being initialized in the constructor, so in
the worst case UDPSocketObject::OnSend() could be called with a bogus
value there.

CID=194757
BUG=XWALK-2928

(cherry picked from commit d2251a745a049543d51f814978c2e20c4934468e)
Merge pull request #2660 from rakuco/cr10-backport-my-own-coverity-fixes

crosswalk-10: Backport my own Coverity fixes.