Refactor chrome's action mode logics and namings

Refactor chrome's action mode logics and namings

ActionMode is the standard naming for the copy-paste-select bar in
android. (http://developer.android.com/guide/topics/ui/menus.html) In
chrome on android, three types of ActionMode exist:
1. ContextualMenuBar and CustomSelectionActionModeCallback. This is for
toolbar and omnibox editing. On tablet, ContextualMenuBar controls the
animation to move toolbar downwards, hiding the tabstrip.
2. SelectionActionModeCallback and SelectionActionMode are content
layer concept for selecting strings inside of the webcontents.
3. ChromeSelectActionModeCallback is the same thing in chrome layer.

To make our naming more clear and more intuitive, several renamings are
proposed in this CL:
1. ContextualMenuBar -> ActionModeController. This class only handles
animation for toolbar, and it is essentially a controller/manager.
2. CustomSelectionActionModeCallback -> ToolbarActionModeCallback. This
callback only serves content editing in toolbar and omnibox.
3. SelectActionMode -> WebActionMode; SelectActionModeCallback ->
WebActionModeCallback. This renaming is to distinguish between
webcontents and android native views.

This CL also removes the unused code in ChromeTabbedActivity.

BUG=521194

Review URL: https://codereview.chromium.org/1292923004

Cr-Commit-Position: refs/heads/master@{#344336}