Implement StructTraits for remaining IndexedDB IPC types.

content/common/indexed_db/indexed_db.mojom

Index: content/common/indexed_db/indexed_db.mojom
diff --git a/content/common/indexed_db/indexed_db.mojom b/content/common/indexed_db/indexed_db.mojom
index b715909b9967a1299bd6577488613056b3a88fdf..2574aa62fcaf494c68dc3c6eb98a51797cf79c2c 100644
--- a/content/common/indexed_db/indexed_db.mojom
+++ b/content/common/indexed_db/indexed_db.mojom
@@ -23,14 +23,44 @@ enum DataLoss {
   Total,
 };
 
-[Native]
-struct Key;
+// Represents key types that hold no data and so cannot be options in the
+// KeyData union.
+enum DatalessKeyType {
+  Invalid,
+  Null,
+};
 
-[Native]
-struct KeyPath;
+union KeyData {
+  array<Key> key_array;
+  array<uint8> binary;
+  mojo.common.mojom.String16 string;
+  double date;
+  double number;
+  DatalessKeyType other;

[jsbell, 2016/11/17 04:32:42]

Ugh. I remember this falling out of very early WebKit implementation. In theory
a Key should be just union {array, binary, string, date, number} and be nullable
in certain places (e.g. KeyRange)

This is probably fine for now but we should add a big TODO to clean this up end
to end.

[Reilly Grant (use Gerrit), 2016/11/17 21:31:17]

Added a little TODO.

+};
 
-[Native]
-struct KeyRange;
+// Defined as a structure so that it can by typemapped with StructTraits.
+struct Key {
+  KeyData data;
+};
+
+// Represents WebIDBKeyPathTypeString and WebIDBKeyPathTypeArray in a key path.
+union KeyPathData {
+  mojo.common.mojom.String16 string;
+  array<mojo.common.mojom.String16> string_array;
+};
+
+struct KeyPath {
+  // A null value here corresponds to WebIDBKeyPathTypeNull.
+  KeyPathData? data;
+};
+
+struct KeyRange {
+  Key lower;
+  Key upper;
+  bool lower_open;
+  bool upper_open;
+};
 
 enum PutMode {
   AddOrUpdate,