Allow Mojo structs as map keys

mojo/public/cpp/bindings/tests/rect_chromium.h

 // Copyright 2015 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_TESTS_RECT_CHROMIUM_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_TESTS_RECT_CHROMIUM_H_
 
 #include "base/logging.h"
 
 namespace mojo {
@@ skipping 37 matching lines @@
   }
 
   int height() const { return height_; }
   void set_height(int height) {
     DCHECK_GE(height, 0);
     height_ = height;
   }
 
   int GetArea() const { return width_ * height_; }
 
+  bool operator==(const RectChromium& other) const {
+    return (x() == other.x() && y() == other.y() && width() == other.width() &&
+            height() == other.height());
+  }
+  bool operator!=(const RectChromium& other) const { return !(*this == other); }
+
  private:
   int x_ = 0;
   int y_ = 0;
   int width_ = 0;
   int height_ = 0;
 };
 
 }  // namespace test
 }  // namespace mojo
 
+namespace std {
+
+template <>
+struct hash<mojo::test::RectChromium> {
+  size_t operator()(const mojo::test::RectChromium& value) {
+    // Terrible hash function:
+    return (std::hash<int>()(value.x()) ^ std::hash<int>()(value.y()) ^
+            std::hash<int>()(value.width()) ^ std::hash<int>()(value.height()));
+  }
+};
+
+}  // namespace std
+
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_TESTS_RECT_CHROMIUM_H_