Remove the 2-level input method system & InputMethodBridge.

This is IMF refactoring according to the design:
 - For @google.com:
  https://docs.google.com/document/d/14PQN4fbbSTlJmIk6qk7RzsuNr7O22DUTfNQ6slxKWV0
 - For @chromium.org:
  https://docs.google.com/document/d/1sDES_kuEVUjb_FwCvKsg0Ef48edq5lAx589r0qUtG4g

This cl includes some fundamental changes:
1) Removed ui/views/ime/...
2) All TextInputClient's use InputMethod::SetFocusedTextInputClient() to inform
   InputMethod that itself is focused.
3) Supports mocking input method in InputMethodFactory for TextfieldTest.
4) Removed views::View::GetTextInputClient() which is useless.
The rest changes follow the above major changes.

BUG=474828
TEST=Verified locally on Win7/Win8/Linux/CrOS/Mac. Tests passed.

Review URL: https://codereview.chromium.org/1177503003

Cr-Commit-Position: refs/heads/master@{#337157}
67 files changed