Revert of Service Manager: Remove ServiceContext* arg from Service::OnStart()

Revert of Service Manager: Remove ServiceContext* arg from Service::OnStart() (patchset #7 id:120001 of https://codereview.chromium.org/2487573002/ )

Reason for revert:
Compile failure, conflicting with another CL

Original issue's description:
> Service Manager: Remove ServiceContext* arg from Service::OnStart()
> 
> This restores the context() accessor to Service, but now
> guarantees that ServiceContext always sets the context
> before invoking OnStart().
> 
> This means that all Service implementations are free to safely
> access context() any time after OnStart() regardless of what
> service-running mechanism was used to create their
> ServiceContext.
> 
> BUG=654986
> 
> Committed: https://crrev.com/6d9b6cd9869d3f8385a42b3272edd7f5b3a6ac5e
> Cr-Commit-Position: refs/heads/master@{#431752}

TBR=ben@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=654986

[Ken Rockot(use gerrit already), 2016-11-12 02:57:04]

The CQ bit was checked by rockot@chromium.org

[Ken Rockot(use gerrit already), 2016-11-12 02:57:05]

Created Revert of Service Manager: Remove ServiceContext* arg from
Service::OnStart()

[commit-bot: I haz the power, 2016-11-12 02:57:32]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-12 02:59:08]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-11-12 02:59:11]

Failed to apply patch for ash/autoclick/mus/autoclick_application.cc:
While running git apply --index -p1;
  error: patch failed: ash/autoclick/mus/autoclick_application.cc:77
  error: ash/autoclick/mus/autoclick_application.cc: patch does not apply

Patch:       ash/autoclick/mus/autoclick_application.cc
Index: ash/autoclick/mus/autoclick_application.cc
diff --git a/ash/autoclick/mus/autoclick_application.cc
b/ash/autoclick/mus/autoclick_application.cc
index
c66ca870997d962a0a007d8eef05dda417866980..6469b79c6b041a0b56fff1acfa7b03f9b0a4c9a1
100644
--- a/ash/autoclick/mus/autoclick_application.cc
+++ b/ash/autoclick/mus/autoclick_application.cc
@@ -77,11 +77,11 @@
 
 AutoclickApplication::~AutoclickApplication() {}
 
-void AutoclickApplication::OnStart() {
+void AutoclickApplication::OnStart(service_manager::ServiceContext* context) {
   aura_init_ = base::MakeUnique<views::AuraInit>(
-      context()->connector(), context()->identity(),
"views_mus_resources.pak");
+      context->connector(), context->identity(), "views_mus_resources.pak");
   window_manager_connection_ = views::WindowManagerConnection::Create(
-      context()->connector(), context()->identity());
+      context->connector(), context->identity());
   autoclick_controller_common_.reset(new AutoclickControllerCommon(
       base::TimeDelta::FromMilliseconds(kDefaultAutoclickDelayMs), this));
 }