Replacing the OVERRIDE with override in tools folder

tools/gn/builder_unittest.cc

Index: tools/gn/builder_unittest.cc
diff --git a/tools/gn/builder_unittest.cc b/tools/gn/builder_unittest.cc
index b9b7e5fb50b75b267ef208426a6c0a88d19eda32..059037d7be946ee883c78a3c5604822351848516 100644
--- a/tools/gn/builder_unittest.cc
+++ b/tools/gn/builder_unittest.cc
@@ -19,16 +19,16 @@ class MockLoader : public Loader {
   // Loader implementation:
   virtual void Load(const SourceFile& file,
                     const LocationRange& origin,
-                    const Label& toolchain_name) OVERRIDE {
+                    const Label& toolchain_name) override {
     files_.push_back(file);
   }
-  virtual void ToolchainLoaded(const Toolchain* toolchain) OVERRIDE {
+  virtual void ToolchainLoaded(const Toolchain* toolchain) override {
   }
-  virtual Label GetDefaultToolchain() const OVERRIDE {
+  virtual Label GetDefaultToolchain() const override {
     return Label();
   }
   virtual const Settings* GetToolchainSettings(
-      const Label& label) const OVERRIDE {
+      const Label& label) const override {
     return NULL;
   }