OAuth2 support for Webstore downloads.

extensions/browser/webstore_oauth2_token_provider.cc

+// Copyright 2014 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.
+
+#include "extensions/browser/webstore_oauth2_token_provider.h"
+
+#include "google_apis/gaia/identity_provider.h"
+
+namespace extensions {
+
+namespace {
+
+const char kChromeWebstoreOAuth2Scope[] =
+    "https://www.googleapis.com/auth/chromewebstore.readonly";
+const char kWebstoreOAuth2TokenConsumerId[] = "webstore-oauth2-token-provider";
+
+}  // namespace
+
+WebstoreOAuth2TokenProvider::WebstoreOAuth2TokenProvider(
+    IdentityProvider* identity_provider)
+    : OAuth2TokenService::Consumer(kWebstoreOAuth2TokenConsumerId),
+      identity_provider_(identity_provider) {
+}
+
+WebstoreOAuth2TokenProvider::~WebstoreOAuth2TokenProvider() {
+}
+
+void WebstoreOAuth2TokenProvider::FetchToken(const FetchCallback& callback) {
+  if (access_token_.empty()) {
+    OAuth2TokenService::ScopeSet scopes;
+    scopes.insert(kChromeWebstoreOAuth2Scope);
+    pending_callbacks_.push(callback);
+    access_token_request_.reset(
+        identity_provider_->GetTokenService()
+            ->StartRequest(
+                  identity_provider_->GetActiveAccountId(), scopes, this)
+            .release());
+  } else {
+    callback.Run(true, access_token_);

[Roger Tawa OOO till Jul 10th, 2014/08/07 01:35:16]

There is no need to optimize the number of calls to StartRequest(), as that is
done already inside O2TS.  That is, multiple requests for the same
account_id/scopes will result in only one request to the server and the
resulting access token is cached.

It would be simpler to just have an |access_token| member in
ExtensionDownloader.  Fetch the token once and then reuse it with each fetcher. 
I'm not sure you need WebstoreOAuth2TokenProvider at all.

When fetching an extension fails due to an auth error, you should call
O2TS::InvalidateToken() and clear the |access_token| member.  Then request a new
access token right away or only when you need it next.  I suspect this should be
done in ExtensionDownloader::OnCRXFetchComplete() but don't know the code well
enough to say.  See web history code for an example:

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/his...

[Ken Rockot(use gerrit already), 2014/08/07 16:49:09]

Aye, this is (sort of) what I was originally doing, but thought it might be
cleaner to separate the O2TS::Consumer implementation from ExtensionDownloader.
In retrospect this did end up being more complex than necessary.

WebstoreOauth2TokenProvider is gone now.

+  }
+}
+
+void WebstoreOAuth2TokenProvider::OnGetTokenSuccess(
+    const OAuth2TokenService::Request* request,
+    const std::string& access_token,
+    const base::Time& expiration_time) {
+  access_token_ = access_token;
+  CallbackQueue callbacks;
+  pending_callbacks_.swap(callbacks);
+  while (!callbacks.empty()) {
+    callbacks.front().Run(true, access_token_);
+    callbacks.pop();
+  }
+}
+
+void WebstoreOAuth2TokenProvider::OnGetTokenFailure(
+    const OAuth2TokenService::Request* request,
+    const GoogleServiceAuthError& error) {
+  CallbackQueue callbacks;
+  pending_callbacks_.swap(callbacks);
+  while (!callbacks.empty()) {
+    callbacks.front().Run(false, "");
+    callbacks.pop();
+  }
+}
+
+}  // namespace extensions