Build SkThreadUtils (home of SkThread type) too.

skia/BUILD.gn

Index: skia/BUILD.gn
diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index edb9b051c9d2e4445a6a2df602b9da3ccdb47780..75c764c0703caeb8b05326a0755d3c152647cfcd 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -382,27 +382,35 @@ component("skia") {
   "//third_party/skia/src/utils/SkPathUtils.cpp",
   "//third_party/skia/src/utils/SkSHA1.cpp",
   "//third_party/skia/src/utils/SkSHA1.h",
-  "//third_party/skia/src/utils/SkThreadUtils.h",
-  "//third_party/skia/src/utils/SkThreadUtils_pthread.cpp",
-  "//third_party/skia/src/utils/SkThreadUtils_pthread.h",
-  "//third_party/skia/src/utils/SkThreadUtils_pthread_linux.cpp",
-  "//third_party/skia/src/utils/SkThreadUtils_pthread_mach.cpp",
-  "//third_party/skia/src/utils/SkThreadUtils_pthread_other.cpp",
-  "//third_party/skia/src/utils/SkThreadUtils_win.cpp",
   "//third_party/skia/src/utils/SkTFitsIn.h",
   "//third_party/skia/src/utils/SkTLogic.h",
 
+  # We don't currently need to change thread affinity, so leave out this complexity for now.
+  "//third_party/skia/src/utils/SkThreadUtils_pthread_mach.cpp",
+  "//third_party/skia/src/utils/SkThreadUtils_pthread_linux.cpp",
+
   #testing
   "//third_party/skia/src/fonts/SkGScalerContext.cpp",
   "//third_party/skia/src/fonts/SkGScalerContext.h",
   ]
 
+  if (is_win) {
+    sources -= [
+      # Keeping _win.cpp
+      "//third_party/skia/src/utils/SkThreadUtils_pthread.cpp",
+      "//third_party/skia/src/utils/SkThreadUtils_pthread_other.cpp",
+    ]
+  } else {
+    sources -= [
+      # Keeping _pthread.cpp and _pthread_other.cpp.
+      "//third_party/skia/src/utils/SkThreadUtils_win.cpp",
+    ]
+  }
+
   # need separate win section to handle chromes auto gn filter
   # (build/config/BUILDCONFIG.gn)
   if (is_win) {
     sources -= [
-      "//third_party/skia/src/utils/SkThreadUtils_win.h",
-
       #windows
       "//third_party/skia/include/utils/win/SkAutoCoInitialize.h",
       "//third_party/skia/include/utils/win/SkHRESULT.h",