Unmap unpinned ashmem regions.                                                                                                                                                                                                                                                                                                 

This partly reverts r229838 and is only a temporary change that will be
reverted soon.

It is needed to stabilize memory metrics so that other regressions can be
caught.

BUG=311633

Review URL: https://codereview.chromium.org/52303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232081 0039d316-1c4b-4281-b951-d872f2087c98
WebRequest: Document listeners always getting statusLine

Listeners registered to a couple of the WebRequest API events get a 'details' argument, which always contains the 'statusLine' argument.

It used to be marked as optional, but it's actually always set. This CL drops the optional flag, and adds more explanation about what is the value. This way extension developers may rely on details.statusLine being defined.

BUG=284017

Review URL: https://codereview.chromium.org/52483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232082 0039d316-1c4b-4281-b951-d872f2087c98
Cast: fix resending audio ACKs.

Review URL: https://codereview.chromium.org/53513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232083 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232082
SVN changes up to revision 232083