GitLab

Extracting the launching code that will go to base from
ChildProcessLauncherHelper (CPLH) to ChildProcessLauncher (CPL).
CPLH now creates a CPL that takes care of creating the connection and
setting it up and delegates back to the CPLH for content specific behavior.

Adding tests to validate the CPL API and moving some existing tests to
use CPL instead of CPLH. The new tests use a new test service
(TestChildProcessService) that echoes back the delegate calls called
on it.  
Also removing the CPLH tests validating strong binding connections as
this is already tested in ChildConnectionAllocatorTest.

Bug: 702316
Change-Id: Ic2bda3f621530616cacc60e22007ca36464a0159
Reviewed-on: https://chromium-review.googlesource.com/557890
Commit-Queue: Jay Civelli <jcivelli@chromium.org>
Reviewed-by: Bo Liu <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485140}