[clang-tidy] new google-default-arguments check

Summary:
To check the google style guide rule here:
https://google.github.io/styleguide/cppguide.html#Default_Arguments

Patch by Clement Courbet!

Reviewers: hokein

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D19534

llvm-svn: 268919
diff --git a/clang-tools-extra/test/clang-tidy/google-default-arguments.cpp b/clang-tools-extra/test/clang-tidy/google-default-arguments.cpp
new file mode 100644
index 0000000..48d3f2d
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/google-default-arguments.cpp
@@ -0,0 +1,29 @@
+// RUN: %check_clang_tidy %s google-default-arguments %t
+
+struct A {
+  virtual void f(int I, int J = 3);
+  // CHECK-MESSAGES: :[[@LINE-1]]:16: warning: default arguments on virtual or override methods are prohibited [google-default-arguments]
+};
+
+struct B : public A {
+  void f(int I, int J = 5);
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: default arguments on virtual or override methods are prohibited
+};
+
+struct C : public B {
+  void f(int I, int J = 5) override;
+  // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: default arguments on virtual or override methods are prohibited
+};
+
+// Negatives.
+struct D : public B {
+  void f(int I, int J) override;
+};
+
+struct X {
+  void f(int I, int J = 3);
+};
+
+struct Y : public X {
+  void f(int I, int J = 5);
+};