Remove LatencyInfo::MergeWith()

Now that we have removed LatencyInfo merging throughout chrome, we
can remove the function LatencyInfo::MergeWith().

Also remove |dump_to_trace| from LatencyInfo::AddLatencyNumberWithTimestamp().
Previously |dump_to_trace| exists because when we merge two LatencyInfo by
calling A.MergeWith(B), we would add B's begin/terminal component into A, which
would accidentally cause TRACE_EVENT_ASYNC_BEGIN/END to be triggered on A. So
that we have |dump_to_trace| to guard against this. Now that we removed MergeWith, we
can also remove |dump_to_trace|.

BUG=246034
TEST=code still compiles.

Review URL: https://codereview.chromium.org/141473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246288 0039d316-1c4b-4281-b951-d872f2087c98
Fix persisted logs not being sent with UMAStability field trial.

This was a bug in http://crrev.com/240919, which introduced
(behind a field trial) the change to send initial crash stats
in a separate log on startup.

There was a problem with that code where it assumed that it
didn't need to load persistent logs when staging the first
histograms log under the new behaviour (field trial).
However, that assumption was only true if we had prepared
the initial stability log (i.e. it was a restart after a
crash). This CL corrects the logic.

BUG=312733

Review URL: https://codereview.chromium.org/141753010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246289 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246288
Remove media's dependency on net

This dependency was added to do a very simple string operation. Now that media
does not depend on net/ via ui/gfx any more, it doesn't make sense to have this
dependency just for this one function.

R=acolwell

Review URL: https://codereview.chromium.org/141863004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246290 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246290