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..3243b42e4357d6c3424bbfe21cfeffc3b3e0eda7 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, 2015/06/16 02:45:03]

Is there any chance to move this logic to TextInputClient::~TextInputClient() ?

One idea to do that would be having two more methods in TextInputClient as
follows.

class TextInputClient {
  ~TextInputClient() {
    if (input_method_)
      input_method_->DetachTextInputClient(this);
  }

  void OnSetFocusedTextInputClient(InputMethod *input_method) {
    CHECK_EQ(nullptr, input_method_);
    input_method_ = input_method;
  }

  void OnDetachTextInputClient(const InputMethod *input_method) {
    CHECK_EQ(input_method, input_method_);
    input_method_ = nullptr;
  }

 private:
  InputMethod* input_method_;  // does not take the ownership.

};

Then we can call them back from InputMethod::SetFocusedTextInputClient and
InputMethod::DetachTextInputClient, respectively.

[Shu Chen, 2015/06/16 05:15:27]

I would prefer not to do that. Currently TextInputClient is defined as a pure
interface.
And bound TextInputClient with InputMethod in bi-direction will bring extra
complexity, e.g. maintain the semantics of "only one TextInputClient can be
focused, and only one TextInputClient can have the valid |input_method_|
instance".

[yukawa, 2015/06/16 05:34:10]

It may make sense but how do you guarantee that GetInputMethod() is still valid
and non-null here?  I'm not worried about the validity of GetInputMethod() in
View::OnFocus() and View::OnBlur(), but I'm not sure what guarantees that
GetInputMethod() still returns non-null object here?

I'm under the impression that object lifetime management and view focus
management are mixed here.

[Shu Chen, 2015/06/16 06:53:59]

GetInputMethod() returns NULL only when the View is out of the views hierarchy.
RemoveChildView() is called in View::~View() so Textfield can get non-null input
method instance in its destructor.
However, there will be a problem if some code take out a Textfield from the
views hierarchy, and destroy it without calling its OnBlur(). But IMO, if
FocusManager can handle the View destruction well, it should call OnBlur()
correctly (e.g. if its |focused_view_| is changed, the old |focused_view_|
should be blurred, before it's destroyed).
I'm not familiar with focus management in Views, can you please share some
insights?

+    GetInputMethod()->DetachTextInputClient(this);
+}
 
 void Textfield::SetReadOnly(bool read_only) {
   // Update read-only without changing the focusable state (or active, etc.).
@@ -715,10 +718,6 @@ bool Textfield::OnKeyPressed(const ui::KeyEvent& event) {
   return handled;
 }
 
-ui::TextInputClient* Textfield::GetTextInputClient() {
-  return this;
-}
-
 void Textfield::OnGestureEvent(ui::GestureEvent* event) {
   switch (event->type()) {
     case ui::ET_GESTURE_TAP_DOWN:
@@ -994,7 +993,8 @@ void Textfield::OnFocus() {
   GetRenderText()->set_focused(true);
   cursor_visible_ = true;
   SchedulePaint();
-  GetInputMethod()->OnFocus();
+  if (GetInputMethod())
+    GetInputMethod()->SetFocusedTextInputClient(this);
   OnCaretBoundsChanged();
 
   const size_t caret_blink_ms = Textfield::GetCaretBlinkMs();
@@ -1010,7 +1010,8 @@ void Textfield::OnFocus() {
 
 void Textfield::OnBlur() {
   GetRenderText()->set_focused(false);
-  GetInputMethod()->OnBlur();
+  if (GetInputMethod())
+    GetInputMethod()->DetachTextInputClient(this);
   cursor_repaint_timer_.Stop();
   if (cursor_visible_) {
     cursor_visible_ = false;
@@ -1459,21 +1460,6 @@ 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;