Remove stray semicolons.

Turns out function declarations don't end in semicolons...

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2720

No public API changes.
TBR=reed@google.com

Change-Id: I72b56d52e1ff7fa6e89c295b0de8c46599791ebb
Reviewed-on: https://skia-review.googlesource.com/2720
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/tools/gpu/gl/null/NullGLTestContext.cpp b/tools/gpu/gl/null/NullGLTestContext.cpp
index 56236a4..dcb6231 100644
--- a/tools/gpu/gl/null/NullGLTestContext.cpp
+++ b/tools/gpu/gl/null/NullGLTestContext.cpp
@@ -21,7 +21,7 @@
    ~NullGLContext() override { this->teardown(); }
 
 private:
-    void onPlatformMakeCurrent() const override {};
+    void onPlatformMakeCurrent() const override {}
     void onPlatformSwapBuffers() const override {}
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
 };