Remove the 2-level input method system & InputMethodBridge.

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index cc2d492a3cb2e1d43c7e4830fd0561637ddc5922..2aa4fe6d8cd06acb845c7dbbff272103a3a18068 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -12,6 +12,7 @@
 #include "ui/base/cursor/cursor.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/drag_utils.h"
+#include "ui/base/ime/input_method.h"
 #include "ui/base/touch/selection_bound.h"
 #include "ui/base/ui_base_switches_util.h"
 #include "ui/compositor/canvas_painter.h"
@@ -31,7 +32,6 @@
 #include "ui/views/controls/native/native_view_host.h"
 #include "ui/views/controls/textfield/textfield_controller.h"
 #include "ui/views/drag_utils.h"
-#include "ui/views/ime/input_method.h"
 #include "ui/views/metrics.h"
 #include "ui/views/native_cursor.h"
 #include "ui/views/painter.h"
@@ -291,7 +291,10 @@ Textfield::Textfield()
   }
 }
 
-Textfield::~Textfield() {}
+Textfield::~Textfield() {
+  if (GetInputMethod())

[yukawa, 2015/06/11 21:48:42]

Why do we test GetTextInputClient() in Combobox::~Combobox() but not in
Textfield::~Textfield()?

Combobox::~Combobox() {
  model_->RemoveObserver(this);
  if (GetTextInputClient() && GetInputMethod())
    GetInputMethod()->DetachTextInputClient(GetTextInputClient());
}

Since neither Textfield nor Textfield::GetTextInputClient() is marked as final,
so in theory you can override Textfield::GetTextInputClient() to return null.

BTW, if you create a derived class of Textfield, who is responsible to call
GetInputMethod()->DetachTextInputClient() ?  Can we put those clean-up code in
more common place?

[Shu Chen, 2015/06/12 03:34:38]

You're right. I've updated the code to check GetTextInputClient().
The derived class of Textfield should be responsible to call
GetInputMethod()->DetachTextInputClient().
And, no, we cannot put this code in common place.

I used to put it in View::~View(), but it caused test failures.
The reason was Combobox::GetTextInputClient() returns PrefixSelector instance:
  ui::TextInputClient* Combobox::GetTextInputClient() {
    if (!selector_)
      selector_.reset(new PrefixSelector(this));
    return selector_.get();
  }
So when destructing Combobox, |selector_| is destructed before its parent's
destructor (~View) being called.
In View's destructor, GetTextInputClient() will get NULL.

[yukawa, 2015/06/12 05:20:45]

Hmm, if the derived class of TextField calls
|GetInputMethod()->DetachTextInputClient()|, then Textfield::~Textfield() calls
|GetInputMethod()->DetachTextInputClient()| again, right?
Probably it will work, but it sounds a bit confusing.
One idea is that adding
  protected:
    void View::DetachTextInputClient();
and call it from Combobox::~Combobox().  Then we can make sure that View can
simply ignore multiple calls of DetachTextInputClient().

[Shu Chen, 2015/06/12 05:32:54]

I think the derived class of TextField overrides GetTextInputClient() doesn't
make sense.
Because TextField is "kind-of" TextInputClient, thus MyTextField should also be
"kind-of" TextInputClient.
If MyTextField overrides GetTextInputClient() which returns non-this, it
conceptually breaks the "kind-of" assumption.
There is no problem to call GetInputMethod()->DetachTextInputClient() for
multiple times, because ui::InputMethodBase's logic can handle it very well.
Ditto. ui::InputMethodBase's logic can handle multiple DetachTextInputClient
calls very well.

+    GetInputMethod()->DetachTextInputClient(GetTextInputClient());
+}
 
 void Textfield::SetReadOnly(bool read_only) {
   // Update read-only without changing the focusable state (or active, etc.).
@@ -994,7 +997,8 @@ void Textfield::OnFocus() {
   GetRenderText()->set_focused(true);
   cursor_visible_ = true;
   SchedulePaint();
-  GetInputMethod()->OnFocus();
+  if (GetInputMethod())

[yukawa, 2015/06/11 21:48:42]

ditto.

[Shu Chen, 2015/06/12 03:34:38]

Done.

+    GetInputMethod()->SetFocusedTextInputClient(this);
   OnCaretBoundsChanged();
 
   const size_t caret_blink_ms = Textfield::GetCaretBlinkMs();
@@ -1010,7 +1014,8 @@ void Textfield::OnFocus() {
 
 void Textfield::OnBlur() {
   GetRenderText()->set_focused(false);
-  GetInputMethod()->OnBlur();
+  if (GetInputMethod())

[yukawa, 2015/06/11 21:48:42]

ditto.

[Shu Chen, 2015/06/12 03:34:38]

Done.

+    GetInputMethod()->DetachTextInputClient(this);
   cursor_repaint_timer_.Stop();
   if (cursor_visible_) {
     cursor_visible_ = false;
@@ -1459,21 +1464,6 @@ void Textfield::InsertChar(base::char16 ch, int flags) {
   }
 }
 
-gfx::NativeWindow Textfield::GetAttachedWindow() const {
-  // Imagine the following hierarchy.
-  //   [NativeWidget A] - FocusManager
-  //     [View]
-  //     [NativeWidget B]
-  //       [View]
-  //         [View X]
-  // An important thing is that [NativeWidget A] owns Win32 input focus even
-  // when [View X] is logically focused by FocusManager. As a result, an Win32
-  // IME may want to interact with the native view of [NativeWidget A] rather
-  // than that of [NativeWidget B]. This is why we need to call
-  // GetTopLevelWidget() here.
-  return GetWidget()->GetTopLevelWidget()->GetNativeWindow();
-}
-
 ui::TextInputType Textfield::GetTextInputType() const {
   if (read_only() || !enabled())
     return ui::TEXT_INPUT_TYPE_NONE;