chrome/blink: Add functionality for in-product help for media elements.

chrome/common/media_iph.mojom

+// Copyright 2017 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 chrome.mojom;
+
+import "ui/gfx/geometry/mojo/geometry.mojom";
+
+// Browser-side service used by the renderer for showing the IPH UI widget/popup
+// for the media download button.
+interface MediaIPHService {
+  // The position of the button in the frame's local coordinate space, where the
+  // UI widget should be anchored.
+  ShowIPHWidget(gfx.mojom.Rect button_rect, bool new_request);
+  
+  // Hide the widget currently being shown for this frame.
+  HideIPHWidget();
+};
+
+// Renderer-side service to listen to notifications when the UI widget on the
+// browser is dismissed/removed.
+interface MediaIPHDelegateService {
+  // Informs the renderer that the UI widget shown for this button in the
+  // browser was dismissed.
+  WidgetDismissed();
+};