Add TaskPriority as a parameter to SequencedWorkerPool in preparation for TaskScheduler experiment.

services/shell/standalone/context.cc

Index: services/shell/standalone/context.cc
diff --git a/services/shell/standalone/context.cc b/services/shell/standalone/context.cc
index 47565d6a3247a974e0a4fddcf51545e9b2ece095..3b1b979f5911c95aa99d3046cd7e9967845b9409 100644
--- a/services/shell/standalone/context.cc
+++ b/services/shell/standalone/context.cc
@@ -137,8 +137,8 @@ void Context::Init(std::unique_ptr<InitParams> init_params) {
     EnsureEmbedderIsInitialized();
 
   shell_runner_ = base::ThreadTaskRunnerHandle::Get();
-  blocking_pool_ =
-      new base::SequencedWorkerPool(kMaxBlockingPoolThreads, "blocking_pool");
+  blocking_pool_ = new base::SequencedWorkerPool(
+      kMaxBlockingPoolThreads, "blocking_pool", base::TaskPriority::BACKGROUND);

[jam, 2016/06/22 20:17:37]

similarly, i don't think this should be priority. when the mojo shell is reading
manifests (note, this isn't in production at the moment), it's blocked on
loading apps' manifest.

[gab, 2016/06/22 21:08:56]

Okay then everything but reading manifests should be BACKGROUND? And by virtue
of the comment in the CL description we have to take the maximum priority of all
potential tasks for now (until they are split in multiple task runners instead
of associated to a single pool).

So USER_VISIBLE?

 
   init_edk_ = !init_params || init_params->init_edk;
   if (init_edk_) {