Convert PhotonConversionTrajectorySeedProducerFromSingleLeg to stream Producer

[Dr15Jones]

Static analyzer and helgrind show it is safe to convert this class
to be a stream based Producer. Thread performance analysis showed
this conversion is needed for efficient threading.

[Dr15Jones]

This change is purely technical and has no effect on single-threaded running.

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for CMSSW_7_1_X.

Convert PhotonConversionTrajectorySeedProducerFromSingleLeg to stream Producer

It involves the following packages:

RecoTracker/ConversionSeedGenerators

@nclopezo, @cmsbuild, @Degano, @StoyanStoynev, @slava77 can you please review it and eventually sign? Thanks.
@ghellwig, @GiacomoSguazzoni, @rovere, @gpetruc, @cerati, @venturia this is something you requested to watch as well.
You can sign-off by replying to this message having '+1' in the first line of your reply.
You can reject by replying to this message having '-1' in the first line of your reply.
@nclopezo, @ktf you are the release manager for this.
You can merge this pull request by typing 'merge' in the first line of your comment.

[cmsbuild]

+1
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4089/1647/summary.html

[slava77]

+1

for #4089 dbc734c

jenkins ok

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_1_X IBs unless changes (tests are also fine). @nclopezo, @ktf can you please take care of it?

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4089/1647/summary.html

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-4089/1647/summary.html