Redesigns the text input focus handling.

ui/wm/core/focus_controller.cc

Index: ui/wm/core/focus_controller.cc
diff --git a/ui/wm/core/focus_controller.cc b/ui/wm/core/focus_controller.cc
index f4d3f3fb8feaa1502400d40ca3c0266cce9bab95..37af32e6ea2f17130be79b5d0d0745c408077274 100644
--- a/ui/wm/core/focus_controller.cc
+++ b/ui/wm/core/focus_controller.cc
@@ -10,6 +10,7 @@
 #include "ui/aura/client/focus_change_observer.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window_tracker.h"
+#include "ui/base/ime/text_input_focus_manager.h"
 #include "ui/events/event.h"
 #include "ui/wm/core/focus_rules.h"
 #include "ui/wm/core/window_util.h"
@@ -230,6 +231,15 @@ void FocusController::SetFocusedWindow(aura::Window* window) {
 
   base::AutoReset<bool> updating_focus(&updating_focus_, true);
   aura::Window* lost_focus = focused_window_;
+
+  // |window| is going to get the focus, so reset the text input client.
+  // OnWindowFocused() may set a proper text input client if the implementation
+  // supports text input.
+  ui::TextInputFocusManager* text_input_focus_manager =
+      ui::TextInputFocusManager::GetInstance();
+  if (window)
+    text_input_focus_manager->FocusTextInputClient(NULL);
+
   // Allow for the window losing focus to be deleted during dispatch. If it is
   // deleted pass NULL to observers instead of a deleted window.
   aura::WindowTracker window_tracker;
@@ -261,6 +271,10 @@ void FocusController::SetFocusedWindow(aura::Window* window) {
         focused_window_,
         window_tracker.Contains(lost_focus) ? lost_focus : NULL);
   }
+
+  // Ensure that the text input client is reset when the window loses the focus.
+  if (!window)
+    text_input_focus_manager->FocusTextInputClient(NULL);

[msw, 2014/05/02 18:46:03]

nit: the value of |window| doesn't change from line 240, afaict. Is it possible
to just call text_input_focus_manager->FocusTextInputClient(NULL); once above,
regardless of the value of |window|? Perhaps I'm missing some nuance here.

[Yuki, 2014/05/07 05:58:02]

Some observers above might change the focused text input client (if so, it must
be NULL though), we'd like to make sure here that the focused text input client
is NULL when losing the window focus regardless of observer's behavior.

 }
 
 void FocusController::SetActiveWindow(aura::Window* requested_window,