Revert of Remove SkThread.h, include SkMutex.h or SkAtomics.h as appropriate.

src/core/SkDrawable.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#include "SkAtomics.h"
 #include "SkCanvas.h"
 #include "SkDrawable.h"
+#include "SkThread.h"
 
 static int32_t next_generation_id() {
     static int32_t gCanvasDrawableGenerationID;
 
     // do a loop in case our global wraps around, as we never want to
     // return a 0
     int32_t genID;
     do {
         genID = sk_atomic_inc(&gCanvasDrawableGenerationID) + 1;
     } while (0 == genID);
@@ skipping 47 matching lines @@
     SkPictureRecorder recorder;
 
     const SkRect bounds = this->getBounds();
     SkCanvas* canvas = recorder.beginRecording(bounds, NULL, 0);
     this->draw(canvas);
     if (false) {
         draw_bbox(canvas, bounds);
     }
     return recorder.endRecording();
 }