Revert of Implement ui::ClipboardMus.

components/mus/public/interfaces/clipboard.mojom

 // Copyright 2016 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.
 
 module mus.mojom;
 
-const string kMimeTypeHTML = "text/html";
-const string kMimeTypeMozillaURL = "text/x-moz-url";
-const string kMimeTypePNG = "image/png";
-const string kMimeTypeRTF = "text/rtf";
-const string kMimeTypeText = "text/plain";
-const string kMimeTypeURIList = "text/uri-list";
-const string kMimeTypeURL = "text/url";
-
 interface Clipboard {
   enum Type {
     COPY_PASTE = 0,
     SELECTION = 1,
     DRAG = 2
   };
 
+  // Mime type constants
+  const string MIME_TYPE_TEXT = "text/plain";
+  const string MIME_TYPE_HTML = "text/html";
+  const string MIME_TYPE_URL = "text/url";
+
   // Returns a sequence number which uniquely identifies clipboard state.
   // Clients are able to assume that the clipboard contents are unchanged as
   // long as this number has not changed. This number is monotonically
   // increasing, is increased when the clipboard state changes, and is
   // provided by Windows, Linux, and Mac.
   [Sync]
   GetSequenceNumber(Type clipboard_type) => (uint64 sequence);
 
   // Returns the available mime types, and the current sequence number.
   [Sync]
   GetAvailableMimeTypes(Type clipboard_types)
       => (uint64 sequence, array<string> types);
 
-  // Returns the current data associated with the requested Mime type.
+  // If the current sequence number is still |sequence|, returns true and the
+  // current data associated with the requested Mime type. When the sequence
+  // number has changed (because new data has been written to the clipboard),
+  // returns false and null for |data|.
   //
   // We don't want to provide one API to return the entire clipboard state
   // because the combined size of the clipboard can be megabytes, especially
   // when image data is involved.
   [Sync]
-  ReadClipboardData(Type clipboard_type, string mime_type)
-      => (uint64 sequence, array<uint8>? data);
+  ReadMimeType(uint64 sequence, Type clipboard_type, string mime_type)
+      => (bool sequence_valid, array<uint8>? data);
 
   // Writes a set of mime types to the clipboard. This will increment the
   // sequence number and return that. In the case of an empty or null map,
   // this will just clear the clipboard.
   [Sync]
   WriteClipboardData(Type clipboard_type, map<string, array<uint8>>? data)
       => (uint64 sequence);
 };