Move threadpool code from include/utils to tools/threadpool.

gyp/tools.gyp

Index: gyp/tools.gyp
diff --git a/gyp/tools.gyp b/gyp/tools.gyp
index e16fa4bb7e71bc53a0b7edaa53719b61c46ab3c9..ca62ade7a66d499438d5e1df1b85f3040c5e27f7 100644
--- a/gyp/tools.gyp
+++ b/gyp/tools.gyp
@@ -44,6 +44,19 @@
         ],
       ],
     },
+    {
+      'target_name': 'threadpool',
+      'type': 'static_library',
+      'include_dirs': [ '../tools/threadpool' ],
+      'dependencies': [ 'skia_lib.gyp:skia_lib' ],
+      'sources': [
+        '../tools/threadpool/CondVar.cpp',
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [ '../tools/threadpool' ],
+      },
+    },
+
     {  # This would go in gm.gyp, but it's also used by skimage below.
       'target_name': 'gm_expectations',
       'type': 'static_library',
@@ -170,6 +183,7 @@
       'dependencies': [
         'flags.gyp:flags',
         'skia_lib.gyp:skia_lib',
+        'tools.gyp:threadpool',
       ],
       'cflags': [
         '-O3',