Revert of service worker: Add CHECKs to catch if SWProcessManager isn't...

Revert of service worker: Add CHECKs to catch if SWProcessManager isn't releasing ref counts. (patchset #1 id:1 of https://codereview.chromium.org/2318443002/ )

Reason for revert:
SWProcessManager is innocent. The CHECKs aren't failing.

Original issue's description:
> service worker: Add CHECKs to catch if SWProcessManager isn't releasing ref counts.
>
> We're still not sure where the non-zero ref counts on shutdown come from.
>
> BUG=636377
>
> Committed: https://crrev.com/e7ffbf80d3b612521a7c2564b21b96695586274a
> Cr-Commit-Position: refs/heads/master@{#416596}

TBR=horo@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=636377

Review-Url: https://codereview.chromium.org/2320713003
Cr-Commit-Position: refs/heads/master@{#417472}

content/browser/service_worker/service_worker_process_manager.cc

@@ -193,9 +193,7 @@ void ServiceWorkerProcessManager::AllocateWorkerProcess(
     return;
   }
 
-  // TODO(falken): Revert to DCHECK. Temporary check for debugging
-  // crbug.com/639193
-  CHECK(!base::ContainsKey(instance_info_, embedded_worker_id))
+  DCHECK(!base::ContainsKey(instance_info_, embedded_worker_id))
       << embedded_worker_id << " already has a process allocated";
 
   if (can_use_existing_process) {
@@ -258,9 +256,7 @@ void ServiceWorkerProcessManager::ReleaseWorkerProcess(int embedded_worker_id) {
 
   if (IsShutdown()) {
     // Shutdown already released all instances.
-    // TODO(falken): Revert to DCHECK. Temporary check for debugging
-    // crbug.com/639193
-    CHECK(instance_info_.empty());
+    DCHECK(instance_info_.empty());
     return;
   }
 
@@ -275,16 +271,12 @@ void ServiceWorkerProcessManager::ReleaseWorkerProcess(int embedded_worker_id) {
   RenderProcessHost* rph = NULL;
   if (info->second.site_instance.get()) {
     rph = info->second.site_instance->GetProcess();
-    // TODO(falken): Revert to DCHECK. Temporary check for debugging
-    // crbug.com/639193
-    CHECK_EQ(info->second.process_id, rph->GetID())
+    DCHECK_EQ(info->second.process_id, rph->GetID())
         << "A SiteInstance's process shouldn't get destroyed while we're "
            "holding a reference to it. Was the reference actually held?";
   } else {
-    // TODO(falken): Revert to DCHECK. Temporary check for debugging
-    // crbug.com/639193
     rph = RenderProcessHost::FromID(info->second.process_id);
-    CHECK(rph)
+    DCHECK(rph)
         << "Process " << info->second.process_id
         << " was destroyed unexpectedly. Did we actually hold a reference?";
   }