[Files.app] Prevent an error of non-existing volume on initialization

Previously, if there was a volume which has null entry, the error was occurred and the initialization is not finished correctly. This patch fixes it.

Major changes:
- Combine createFromPath and createFromEntry into create
- Get a path from VolumeInfo, instead of from DirectoryEntry.

BUG=313028
TEST=manually tested

Review URL: https://codereview.chromium.org/63983003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233837 0039d316-1c4b-4281-b951-d872f2087c98
Temporarily crash when a wedge condition is detected.

BUG=316376
TEST=wedge causes a crash.

Review URL: https://codereview.chromium.org/64173007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233838 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233837
SVN changes up to revision 233838