Convert Web Store Inline Install IPCs to mojo

chrome/common/extensions/mojo/inline_install.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 extensions.mojom;
+
+[Native]
+enum WebstoreInstallResult;
+
+[Native]
+enum WebstoreInstallStage;
+
+interface InlineInstallProgressListener {
+  // Notifies the renderer when install stage updates were requested for an
+  // inline install.
+  InlineInstallStageChanged(WebstoreInstallStage stage);
+
+  // Notifies the renderer when download progress updates were requested for an
+  // inline install.
+  InlineInstallDownloadProgress(int32 percent_downloaded);
+};
+
+interface InlineInstall {

[Devlin, 2017/04/28 18:33:02]

nit: maybe InlineInstaller?  WDYT?  (It seems weird to me to have an interface
called InlineInstall, since that makes it sound like it represents the
installation itself)

[catmullings, 2017/05/02 19:02:15]

Done.

+  // Sent by the renderer to implement chrome.webstore.install() and notifies
+  // the renderer once the installation is complete.
+  DoInlineInstall(int32 install_id, string webstore_item_id,

[Devlin, 2017/04/28 18:33:02]

nit: all parameters should have the same indentation (so move install_id and
webstore_item_id to a new line)

[catmullings, 2017/05/02 19:02:15]

Done.

+      int32 listeners_mask,
+      InlineInstallProgressListener install_progress_listener) =>
+      (int32 install_id, bool success, string error,
+      WebstoreInstallResult result);

[catmullings, 2017/05/02 19:02:15]

Documentation:
We removed the callback response on the mojo message because it was causing
WebstoreInlineInstallerTest.NavigateBeforeInstallConfirmation and
WebstoreInlineInstallerTest.CloseTabBeforeInstallConfirmation to fail. In those
tests, inline installation does not complete, so a callback response is never
made, and mojo throws an error. This error check is conducted before the
TabHelper is destroyed.

Because mojo response callbacks do not automatically close the pipe connection,
the following workarounds were considered:  

1.) If there are cases when we know the callback won't be used, then close the
pipe connection
2.) Pass a param to the callback in cases of no-op
3.) Put the callback on a separate interface (i.e. make it a separate mojo msg) 

Option 1 entailed closing the pipe on the webstore installer, which conceptually
wasn't correct since pipe closing should be isolated to the tab helper. The
easiest and simplest solution was option 3. 

+};
+
+