mojom: Add associative arrays to the mojom language.

mojo/services/public/interfaces/clipboard/clipboard.mojom

Index: mojo/services/public/interfaces/clipboard/clipboard.mojom
diff --git a/mojo/services/public/interfaces/clipboard/clipboard.mojom b/mojo/services/public/interfaces/clipboard/clipboard.mojom
index c1e1be4ee09f79244c36d7437d4d918d3e1958c8..3dfec0d4797ea70bc85de249aa89e31eb046bb98 100644
--- a/mojo/services/public/interfaces/clipboard/clipboard.mojom
+++ b/mojo/services/public/interfaces/clipboard/clipboard.mojom
@@ -4,13 +4,6 @@
 
 module mojo {
 
-// A wrapper type which is just a Key/Value pair. Workaround until we get
-// proper maps in mojom.
-struct MimeTypePair {
-  string mime_type;
-  uint8[] data;
-};
-
 interface Clipboard {
   enum Type {
     COPY_PASTE = 0,
@@ -44,9 +37,9 @@ interface Clipboard {
   ReadMimeType(Type clipboard_type, string mime_type) => (uint8[]? data);
 
   // Writes a set of mime types to the clipboard. This will increment the
-  // sequence number. In the case of an empty or NULL list, this will just
+  // sequence number. In the case of an empty map, this will just
   // clear the clipboard.
-  WriteClipboardData(Type clipboard_type, MimeTypePair[]? data);
+  WriteClipboardData(Type clipboard_type, uint8[string][]? data);
 };
 
 }  // module mojo