Allow Mojo structs as map keys

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

Index: mojo/public/cpp/bindings/tests/rect_chromium.h
diff --git a/mojo/public/cpp/bindings/tests/rect_chromium.h b/mojo/public/cpp/bindings/tests/rect_chromium.h
index 20c43628c3ab60d0039491c257e515b7a3a43356..d2e0a3e635b8004021f75f0066c45f2a23b48bb4 100644
--- a/mojo/public/cpp/bindings/tests/rect_chromium.h
+++ b/mojo/public/cpp/bindings/tests/rect_chromium.h
@@ -55,6 +55,12 @@ class RectChromium {
 
   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;
@@ -65,4 +71,17 @@ class RectChromium {
 }  // 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_