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 4dd085c6e05b33fd1b3c8d3609c8a41972008867..ae9613fca51a8ac2bb51e95e37bcdbbcd6e4ae83 100644
--- a/ui/keyboard/keyboard_controller.cc
+++ b/ui/keyboard/keyboard_controller.cc
@@ -6,6 +6,9 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "content/public/browser/render_widget_host.h"
+#include "content/public/browser/render_widget_host_iterator.h"
+#include "content/public/browser/render_widget_host_view.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/base/cursor/cursor.h"
@@ -234,6 +237,16 @@ void KeyboardController::NotifyKeyboardBoundsChanging(
     FOR_EACH_OBSERVER(KeyboardControllerObserver,
                       observer_list_,
                       OnKeyboardBoundsChanging(new_bounds));
+    if (keyboard::IsKeyboardOverscrollEnabled()) {
+      // Adjust the height of the viewport for visible windows on the primary
+      // display.
+      scoped_ptr<content::RenderWidgetHostIterator> widgets(
+          content::RenderWidgetHost::GetRenderWidgetHosts());
+      while (content::RenderWidgetHost* widget = widgets->GetNextHost()) {
+        content::RenderWidgetHostView* view = widget->GetView();
+        view->SetKeyboardBounds(new_bounds);
+      }
+    }
   }
 }