Implement overscroll support for the virtual keyboard.

ui/keyboard/keyboard_controller.cc

Index: ui/keyboard/keyboard_controller.cc
diff --git a/ui/keyboard/keyboard_controller.cc b/ui/keyboard/keyboard_controller.cc
index 95966147d89644c492af6be9e47eb5131752115f..0ae1285286a11cc3b3af5aedfbced9ecbcd5c056 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -6,6 +6,8 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "ui/aura/client/virtual_keyboard_observer.h"
+#include "ui/aura/layout_manager.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/base/cursor/cursor.h"
@@ -17,7 +19,6 @@
 #include "ui/gfx/path.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/skia_util.h"
-#include "ui/keyboard/keyboard_controller_observer.h"
 #include "ui/keyboard/keyboard_controller_proxy.h"
 #include "ui/keyboard/keyboard_layout_manager.h"
 #include "ui/keyboard/keyboard_switches.h"
@@ -217,7 +218,7 @@ aura::Window* KeyboardController::GetContainerWindow() {
 void KeyboardController::NotifyKeyboardBoundsChanging(
     const gfx::Rect& new_bounds) {
   if (proxy_->HasKeyboardWindow() && proxy_->GetKeyboardWindow()->IsVisible()) {
-    FOR_EACH_OBSERVER(KeyboardControllerObserver,
+    FOR_EACH_OBSERVER(aura::client::VirtualKeyboardObserver,
                       observer_list_,
                       OnKeyboardBoundsChanging(new_bounds));
   }
@@ -253,14 +254,20 @@ void KeyboardController::HideKeyboard(HideReason reason) {
   container_->layer()->SetOpacity(kAnimationStartOrAfterHideOpacity);
 }
 
-void KeyboardController::AddObserver(KeyboardControllerObserver* observer) {
+void KeyboardController::AddObserver(
+    aura::client::VirtualKeyboardObserver* observer) {
   observer_list_.AddObserver(observer);
 }
 
-void KeyboardController::RemoveObserver(KeyboardControllerObserver* observer) {
+void KeyboardController::RemoveObserver(
+    aura::client::VirtualKeyboardObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
+bool KeyboardController::IsOverscrollEnabled() {
+  return keyboard::IsKeyboardOverscrollEnabled();
+}
+
 void KeyboardController::ShowAndLockKeyboard() {
   set_lock_keyboard(true);
   OnShowImeIfNeeded();