Add InputMethodObserver support into InputMethodBase

ui/base/ime/input_method_imm32.cc

Index: ui/base/ime/input_method_imm32.cc
diff --git a/ui/base/ime/input_method_imm32.cc b/ui/base/ime/input_method_imm32.cc
index 4f17ea9a19bcaf0512925686c5acd292f3ff8531..ca02fa3e37321c67a8d7ae7dc73432e8597f4979 100644
--- a/ui/base/ime/input_method_imm32.cc
+++ b/ui/base/ime/input_method_imm32.cc
@@ -94,26 +94,23 @@ void InputMethodIMM32::OnTextInputTypeChanged(const TextInputClient* client) {
 }
 
 void InputMethodIMM32::OnCaretBoundsChanged(const TextInputClient* client) {
-  if (!enabled_ || !IsTextInputClientFocused(client) ||
-      !IsWindowFocused(client)) {
-    return;
+  if (enabled_ && IsTextInputClientFocused(client) && IsWindowFocused(client)) {
+    // The current text input type should not be NONE if |client| is focused.
+    DCHECK(!IsTextInputTypeNone());
+    gfx::Rect screen_bounds(GetTextInputClient()->GetCaretBounds());
+
+    HWND attached_window = GetAttachedWindowHandle(client);
+    // TODO(ime): see comment in TextInputClient::GetCaretBounds(), this
+    // conversion shouldn't be necessary.
+    RECT r = {};
+    GetClientRect(attached_window, &r);
+    POINT window_point = { screen_bounds.x(), screen_bounds.y() };
+    ScreenToClient(attached_window, &window_point);
+    gfx::Rect caret_rect(gfx::Point(window_point.x, window_point.y),
+                         screen_bounds.size());
+    imm32_manager_.UpdateCaretRect(attached_window, caret_rect);
   }
-
-  // The current text input type should not be NONE if |client| is focused.
-  DCHECK(!IsTextInputTypeNone());
-  gfx::Rect screen_bounds(GetTextInputClient()->GetCaretBounds());
-
-  HWND attached_window = GetAttachedWindowHandle(client);
-  // TODO(ime): see comment in TextInputClient::GetCaretBounds(), this
-  // conversion shouldn't be necessary.
-  RECT r;
-  GetClientRect(attached_window, &r);
-  POINT window_point = { screen_bounds.x(), screen_bounds.y() };
-  ScreenToClient(attached_window, &window_point);
-  imm32_manager_.UpdateCaretRect(
-      attached_window,
-      gfx::Rect(gfx::Point(window_point.x, window_point.y),
-                screen_bounds.size()));
+  InputMethodWin::OnCaretBoundsChanged(client);
 }
 
 void InputMethodIMM32::CancelComposition(const TextInputClient* client) {