Make leak counters thread-safe

gm/colormatrix.cpp

Index: gm/colormatrix.cpp
diff --git a/gm/colormatrix.cpp b/gm/colormatrix.cpp
index 9ab65630400e2af30ef5be564cfea7c25638d9f7..2f98693da22452858f613a1877567d6a17211bab 100644
--- a/gm/colormatrix.cpp
+++ b/gm/colormatrix.cpp
@@ -12,9 +12,9 @@
 #define WIDTH 500
 #define HEIGHT 500
 
-class SkOnce {
+class SkDoOnce {
 public:
-    SkOnce() : fOnce(false) {};
+    SkDoOnce() : fOnce(false) {};
 
     bool once() const {
         if (fOnce) {
@@ -39,7 +39,7 @@ static void setArray(SkPaint* paint, const SkScalar array[]) {
 namespace skiagm {
 
 class ColorMatrixGM : public GM {
-    SkOnce fOnce;
+    SkDoOnce fOnce;
     void init() {
         if (fOnce.once()) {
             fSolidBitmap = this->createSolidBitmap(64, 64);