Limit usage of full paths during initialization of Files app.

This patch being a part of big full path -> Entry migration effords, converts the default path to an entry as soon as possible, and makes the file_manager.js call the directory model with Entry objects instead.

In general this CL:
- Merges directory_model.js/setupPath() with file_manager.js/setupCurrentDirectory_()
- Converts defaultPath to Entry as soon as the volume manager is available.
- Opens the directory and sets the selection using Entry objects only.

TEST=Tested manually with standalone, and save-as dialog. Also, partly covered by browser tests.
BUG=323753

Review URL: https://codereview.chromium.org/90773002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238057 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238057
Delete unused functions of CandidateWindowController.

BUG=N/A

Review URL: https://codereview.chromium.org/97023002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238058 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238058
[SyncFS] Don't start listing remote change before initialization

BUG=240165

Review URL: https://codereview.chromium.org/97773002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238059 0039d316-1c4b-4281-b951-d872f2087c98
Implement LocalFileChangeTracker::ResetForFileSystem for remote root deletion

When a DELETE change for the root file system comes for a remote sync, I'm planning to call:
1. DeleteFileSystem to delete the entire filesystem data
2. Call this to reset all changes for the filesystem, and
3. OpenFileSystem to reopen the filesystem

BUG=324697
TEST=LocalFileChangeTrackerTest.ResetForFileSystem
R=nhiroki@chromium.org, tzik@chromium.org

Review URL: https://codereview.chromium.org/98493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238060 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238059
Add CandidateClicked to observer.

I am merging IBusEngineHander to InputMethodManager. This is a step of the merge.

BUG=N/A

Review URL: https://codereview.chromium.org/97843002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238061 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238061