Revert of Add dimming to the background during sign in (patchset #4 id:160001 of https://codereview.chromium.org/1400153002/ )

Reason for revert:
https://code.google.com/p/chromium/issues/detail?id=547178

Original issue's description:
> Add dimming to the background during sign in
>
> * Add option to put the dim layer at the bottom. Login screen put this dim layer at the bottom of login container containers so that
>  dim layer stays during login transition.
>
> BUG=478438
> TEST=ScreenDimmer.DimAtBottom
>
> Committed: https://crrev.com/c527600749bfc6970ba39e4ed6b24404b0f7b256
> Cr-Commit-Position: refs/heads/master@{#355481}

TBR=dzhioev@chromium.org,alemate@chromium.org,oshima@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=478438

Review URL: https://codereview.chromium.org/1424513003

Cr-Commit-Position: refs/heads/master@{#355885}

3 files changed, 2 insertions, 37 deletions

diff --git a/ash/wm/screen_dimmer.cc b/ash/wm/screen_dimmer.cc
index 559faaf..6c74888 100644
--- a/ash/wm/screen_dimmer.cc
+++ b/ash/wm/screen_dimmer.cc
@@ -53,10 +53,7 @@ ScreenDimmer* ScreenDimmer::GetForRoot() {
 }
 
 ScreenDimmer::ScreenDimmer(int container_id)
-    : container_id_(container_id),
-      target_opacity_(0.5f),
-      is_dimming_(false),
-      at_bottom_(false) {
+    : container_id_(container_id), target_opacity_(0.5f), is_dimming_(false) {
   Shell::GetInstance()->AddShellObserver(this);
 }
 
@@ -96,10 +93,6 @@ void ScreenDimmer::Update(bool should_dim) {
         dim = new DimWindow(container);
         dim->SetDimOpacity(target_opacity_);
       }
-      if (at_bottom_)
-        dim->parent()->StackChildAtBottom(dim);
-      else
-        dim->parent()->StackChildAtTop(dim);
       dim->Show();
     } else {
       if (dim) {
diff --git a/ash/wm/screen_dimmer.h b/ash/wm/screen_dimmer.h
index 9d8779e..6d26e68 100644
--- a/ash/wm/screen_dimmer.h
+++ b/ash/wm/screen_dimmer.h
@@ -41,8 +41,6 @@ class ASH_EXPORT ScreenDimmer : ShellObserver {
   // Dim or undim the layers.
   void SetDimming(bool should_dim);
 
-  void set_at_bottom(bool at_bottom) { at_bottom_ = at_bottom; }
-
   bool is_dimming() const { return is_dimming_; }
 
   // Find a ScreenDimmer in the container, or nullptr if it does not exist.
@@ -65,7 +63,6 @@ class ASH_EXPORT ScreenDimmer : ShellObserver {
 
   // Are we currently dimming the screen?
   bool is_dimming_;
-  bool at_bottom_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenDimmer);
 };
diff --git a/ash/wm/screen_dimmer_unittest.cc b/ash/wm/screen_dimmer_unittest.cc
index 084105e..9b1bdc6 100644
--- a/ash/wm/screen_dimmer_unittest.cc
+++ b/ash/wm/screen_dimmer_unittest.cc
@@ -10,8 +10,7 @@
 #include "ash/wm/dim_window.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-//#include "ui/aura/window_event_dispatcher.h"
-#include "ui/aura/test/test_windows.h"
+#include "ui/aura/window_event_dispatcher.h"
 #include "ui/compositor/layer.h"
 
 namespace ash {
@@ -87,29 +86,5 @@ TEST_F(ScreenDimmerTest, RootDimmer) {
   EXPECT_EQ(nullptr, ScreenDimmer::FindForTest(-1));
 }
 
-TEST_F(ScreenDimmerTest, DimAtBottom) {
-  ScreenDimmer* root_dimmer = ScreenDimmer::GetForRoot();
-  aura::Window* root_window = Shell::GetPrimaryRootWindow();
-  scoped_ptr<aura::Window> window(
-      aura::test::CreateTestWindowWithId(1, root_window));
-  root_dimmer->SetDimming(true);
-  std::vector<aura::Window*>::const_iterator dim_iter =
-      std::find(root_window->children().begin(), root_window->children().end(),
-                GetDimWindow());
-  ASSERT_TRUE(dim_iter != root_window->children().end());
-  // Dim layer is at top.
-  EXPECT_EQ(*dim_iter, *root_window->children().rbegin());
-
-  root_dimmer->SetDimming(false);
-  root_dimmer->set_at_bottom(true);
-  root_dimmer->SetDimming(true);
-
-  dim_iter = std::find(root_window->children().begin(),
-                       root_window->children().end(), GetDimWindow());
-  ASSERT_TRUE(dim_iter != root_window->children().end());
-  // Dom layer is at the bottom.
-  EXPECT_EQ(*dim_iter, *root_window->children().begin());
-}
-
 }  // namespace test
 }  // namespace ash