Add a background timing thread to kilobench

src/gpu/gl/SkGLContext.cpp

Index: src/gpu/gl/SkGLContext.cpp
diff --git a/src/gpu/gl/SkGLContext.cpp b/src/gpu/gl/SkGLContext.cpp
index ad119aee6a30fa99ee2c8a31767bff0c62d6e320..3169c27ab7afec6cd9d93246d628bf7c26ecc36f 100644
--- a/src/gpu/gl/SkGLContext.cpp
+++ b/src/gpu/gl/SkGLContext.cpp
@@ -77,8 +77,8 @@ void SkGLContext::makeCurrent() const {
     this->onPlatformMakeCurrent();
 }
 
-void SkGLContext::swapBuffers() {
-    if (!fFenceSync) {
+void SkGLContext::swapBuffers(bool usePlatformSwapBuffers) {
+    if (!fFenceSync || usePlatformSwapBuffers) {
         // Fallback on the platform SwapBuffers method for synchronization. This may have no effect.
         this->onPlatformSwapBuffers();
         return;