Windows precompiled header support in GN

tools/gn/test_with_scope.h

Index: tools/gn/test_with_scope.h
diff --git a/tools/gn/test_with_scope.h b/tools/gn/test_with_scope.h
index 79c6a08b32927740bce32db35254875855e982bd..e390df84a59735d9433e8983d9b52a6a575fafad 100644
--- a/tools/gn/test_with_scope.h
+++ b/tools/gn/test_with_scope.h
@@ -43,9 +43,14 @@ class TestWithScope {
   // Fills in the tools for the given toolchain with reasonable default values.
   // The toolchain in this object will be automatically set up with this
   // function, it is exposed to allow tests to get the same functionality for
-  // other toolchains they make
+  // other toolchains they make.
   static void SetupToolchain(Toolchain* toolchain);
 
+  // Sets the given text command on the given tool, parsing it as a
+  // substitution pattern. This will assert if the input is malformed. This is
+  // designed to help setting up Tools for tests.
+  static void SetCommandForTool(const std::string& cmd, Tool* tool);
+
  private:
   void AppendPrintOutput(const std::string& str);