Combine GPU flush with semaphore API

Bug: skia:
Change-Id: I5f388760d43b19755b2767d95d32065f6d0f926e
Reviewed-on: https://skia-review.googlesource.com/14646
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/tools/gpu/GrTest.cpp b/tools/gpu/GrTest.cpp
index 2e34d2f..5582a25 100644
--- a/tools/gpu/GrTest.cpp
+++ b/tools/gpu/GrTest.cpp
@@ -330,10 +330,9 @@
     GrFence SK_WARN_UNUSED_RESULT insertFence() override { return 0; }
     bool waitFence(GrFence, uint64_t) override { return true; }
     void deleteFence(GrFence) const override {}
-    void flush() override {}
 
     sk_sp<GrSemaphore> SK_WARN_UNUSED_RESULT makeSemaphore() override { return nullptr; }
-    void insertSemaphore(sk_sp<GrSemaphore> semaphore) override {}
+    void insertSemaphore(sk_sp<GrSemaphore> semaphore, bool flush) override {}
     void waitSemaphore(sk_sp<GrSemaphore> semaphore) override {}
 
 private: