Update from chromium https://crrev.com/302282

tools/clang/plugins/tests/virtual_specifiers.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Tests for chromium style checks for virtual/override/final specifiers on
 // virtual methods.
 
 // Purposely use macros to test that the FixIt hints don't try to remove the
 // macro body.
 #define OVERRIDE override
@@ skipping 44 matching lines @@
   virtual ~VirtualAndOverrideFinal() OVERRIDE FINAL {}
   virtual void F() OVERRIDE FINAL {}
 };
 
 class OverrideAndFinal : public Base {
  public:
   ~OverrideAndFinal() OVERRIDE FINAL {}
   void F() OVERRIDE FINAL {}
 };
 
+// Also warn on pure functions.
+class CorrectPureVirtual : public Base {
+  virtual void F() = 0;
+};
+
+class Pure : public Base {
+  void F() = 0;
+};
+
+class PureOverride : public Base {
+  void F() override = 0;
+};
+
+class PureVirtualOverride : public Base {
+  virtual void F() override = 0;
+};
+
 // Finally, some simple sanity tests that overrides in the testing namespace
 // don't trigger warnings, except for testing::Test.
 namespace testing {
 
 class Test {
  public:
   virtual ~Test();
   virtual void SetUp();
 };
 
 class NotTest {
  public:
   virtual ~NotTest();
   virtual void SetUp();
 };
 
 }  // namespace
 
 class MyTest : public testing::Test {
  public:
   virtual ~MyTest();
   virtual void SetUp() override;
 };
 
 class MyNotTest : public testing::NotTest {
  public:
   virtual ~MyNotTest();
   virtual void SetUp() override;
 };