Surfaces: Receive resources only once

cc/resources/returned_resource.h

Index: cc/resources/returned_resource.h
diff --git a/cc/resources/returned_resource.h b/cc/resources/returned_resource.h
index 35de506a80621469353104d50a90aff5217c541c..6fb4af7b5b6889bdf9b51a560e5cbd2396255dfb 100644
--- a/cc/resources/returned_resource.h
+++ b/cc/resources/returned_resource.h
@@ -18,6 +18,16 @@ namespace cc {
 // first passed to the parent compositor.
 struct CC_EXPORT ReturnedResource {
   ReturnedResource() : id(0), count(0), lost(false) {}
+
+  bool operator==(const ReturnedResource& other) const {
+    return id == other.id && sync_token == other.sync_token &&
+           count == other.count && lost == other.lost;
+  }
+
+  bool operator!=(const ReturnedResource& other) const {
+    return !(*this == other);
+  }
+
   // |id| is an identifier generated by the child compositor that uniquely
   // identifies a resource. This is the same ID space as TransferableResource.
   ResourceId id;