Fix cropped floating gesture candidate window

This CL introduces ShouldWindowOverscroll function in
keyboard_controller_proxy to check if a window should
be overscrolled. There are two types of window that we
want to avoid overscroll all the time: virtual keyboard
window and ime windows. Ime windows are created by
chrome.app.window.create API. This window is used to
show gesture typing candidate or accents characters.
These two type of windows have the same parent, which is
kShellWindowId_ImeWindowParentContainer top level window.
To disable overscroll, this CL check if a window is a child of
the toplevel window and avoid set overscroll insets if it is.

BUG=529880

Review URL: https://codereview.chromium.org/1323053005

Cr-Commit-Position: refs/heads/master@{#354055}

2 files changed, 5 insertions, 0 deletions

diff --git a/ash/test/test_keyboard_ui.cc b/ash/test/test_keyboard_ui.cc
index b99266c..67b6993 100644
--- a/ash/test/test_keyboard_ui.cc
+++ b/ash/test/test_keyboard_ui.cc
@@ -20,6 +20,10 @@ bool TestKeyboardUI::HasKeyboardWindow() const {
   return keyboard_;
 }
 
+bool TestKeyboardUI::ShouldWindowOverscroll(aura::Window* window) const {
+  return true;
+}
+
 aura::Window* TestKeyboardUI::GetKeyboardWindow() {
   if (!keyboard_) {
     keyboard_.reset(new aura::Window(&delegate_));
diff --git a/ash/test/test_keyboard_ui.h b/ash/test/test_keyboard_ui.h
index d1c1f75..2b8a24e 100644
--- a/ash/test/test_keyboard_ui.h
+++ b/ash/test/test_keyboard_ui.h
@@ -22,6 +22,7 @@ class TestKeyboardUI : public keyboard::KeyboardUI {
   ~TestKeyboardUI() override;
 
   bool HasKeyboardWindow() const override;
+  bool ShouldWindowOverscroll(aura::Window* window) const override;
   aura::Window* GetKeyboardWindow() override;
 
  private: