Revert of SkThreadPool ~~> SkTaskGroup (patchset #4 id:60001 of https://codereview.chromium.org/531653002/)

Reason for revert:
Leaks, leaks, leaks.

Original issue's description:
> SkThreadPool ~~> SkTaskGroup
>
> SkTaskGroup is like SkThreadPool except the threads stay in
> one global pool.  Each SkTaskGroup itself is tiny (4 bytes)
> and its wait() method applies only to tasks add()ed to that
> instance, not the whole thread pool.
>
> This means we don't need to bring up new thread pools when
> tests themselves want to use multithreading (e.g. pathops,
> quilt).  We just create a new SkTaskGroup and wait for that
> to complete.  This should be more efficient, and allow us
> to expand where we use threads to really latency sensitive
> places.  E.g. we can probably now use these in nanobench
> for CPU .skp rendering.
>
> Now that all threads are sharing the same pool, I think we
> can remove most of the custom mechanism pathops tests use
> to control threading.  They'll just ride on the global pool
> with all other tests now.
>
> This (temporarily?) removes the GPU multithreading feature
> from DM, which we don't use.
>
> On my desktop, DM runs a little faster (57s -> 55s) in
> Debug, and a lot faster in Release (36s -> 24s).  The bots
> show speedups of similar proportions, cutting more than a
> minute off the N4/Release and Win7/Debug runtimes.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/9c7207b5dc71dc5a96a2eb107d401133333d5b6f

R=caryclark@google.com, bsalomon@google.com, bungeman@google.com, reed@google.com, mtklein@chromium.org
TBR=bsalomon@google.com, bungeman@google.com, caryclark@google.com, mtklein@chromium.org, reed@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/533393002

1 files changed, 0 insertions, 34 deletions

diff --git a/src/utils/SkTaskGroup.h b/src/utils/SkTaskGroup.h
deleted file mode 100644
index af4d47aa97..0000000000
--- a/src/utils/SkTaskGroup.h
+++ /dev/null
@@ -1,34 +0,0 @@
-/*
- * Copyright 2014 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkTaskGroup_DEFINED
-#define SkTaskGroup_DEFINED
-
-#include "SkTypes.h"
-#include "SkRunnable.h"
-
-class SkTaskGroup : SkNoncopyable {
-public:
-    // Call before creating any SkTaskGroup to set the number of threads all SkTaskGroups share.
-    // If not called, we default to the number of system-reported cores.
-    static void SetThreadCount(int);
-
-    SkTaskGroup();
-    ~SkTaskGroup() { this->wait(); }
-
-    // Add a task to this SkTaskGroup.  It will likely run() on another thread.
-    void add(SkRunnable*);
-
-    // Block until all Tasks previously add()ed to this SkTaskGroup have run().
-    // You may safely reuse this SkTaskGroup after wait() returns.
-    void wait();
-
-private:
-    /*atomic*/ int32_t fPending;
-};
-
-#endif//SkTaskGroup_DEFINED