Add chrome.webstore API methods to allow sites to see progress of installation
Add two chrome.webstore API methods for progress updates:
  chrome.webstore.setInstallStageListener(function(string stage))
  - stage is either "downloading" or "installing"
  chrome.webstore.setDownloadProgressListener(function(int percent_downloaded))
Update InstallObserver to have methods for install stages.
Make WebstoreInstaller provide more frequent download updates (current consumers
like WebstoreResult imply this was intended from the start).
BUG=308634

Review URL: https://codereview.chromium.org/175263003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@259483 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/extensions/tab_helper.h b/chrome/browser/extensions/tab_helper.h
index 42603de..dcfa66b 100644
--- a/chrome/browser/extensions/tab_helper.h
+++ b/chrome/browser/extensions/tab_helper.h
@@ -191,7 +191,8 @@
   void OnInlineWebstoreInstall(int install_id,
                                int return_route_id,
                                const std::string& webstore_item_id,
-                               const GURL& requestor_url);
+                               const GURL& requestor_url,
+                               int listeners_mask);
   void OnGetAppInstallState(const GURL& requestor_url,
                             int return_route_id,
                             int callback_id);