Revert of Force calling PostDisplayConfigurationChange() even if earyling out in UpdateDisplays (patchset #4 id:60001 of https://codereview.chromium.org/559213002/)

Reason for revert:
I am reverting this as it resulted in test VirtualKeyboardUsabilityExperimentTest.VirtualKeyboardWindowTest consistently crashing on Linux ChromiumOS Tests, see:

http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/31731
http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20(1)/builds/2914

Stack trace:

Objects involved in the operation:
sequence "this" @ 0x0x3e568fbdcc90 {
}
Received signal 6
#0 0x7fcb9c8936fe base::debug::StackTrace::StackTrace()
#1 0x7fcb9c893230 base::debug::(anonymous namespace)::StackDumpSignalHandler()
#2 0x7fcb8c474cb0 \u003Cunknown>
#3 0x7fcb8bbc4425 gsignal
#4 0x7fcb8bbc7b8b abort
#5 0x7fcb8c1c75ad __gnu_debug::_Error_formatter::_M_error()
#6 0x7fcb9a306513 std::__debug::vector\u003C>::operator[]()
#7 0x7fcb9a2fbba9 ash::DisplayManager::GetCurrentDisplayIdPair()
#8 0x7fcb9a2d96cf ash::DisplayController::PostDisplayConfigurationChange()
#9 0x7fcb9a2d98bc ash::DisplayController::PostDisplayConfigurationChange()
#10 0x7fcb9a2fd22a ash::DisplayManager::UpdateDisplays()
#11 0x7fcb9a2fdbe8 ash::DisplayManager::SetDisplayRotation()
#12 0x7fcb9a33425b ash::VirtualKeyboardWindowController::FlipDisplay()
#13 0x7fcb9a3340d7 ash::VirtualKeyboardWindowController::UpdateWindow()
#14 0x7fcb9a2d92df ash::DisplayController::CreateOrUpdateNonDesktopDisplay()
#15 0x7fcb9a2d937f ash::DisplayController::CreateOrUpdateNonDesktopDisplay()
#16 0x7fcb9a300ea9 ash::(anonymous namespace)::NonDesktopDisplayUpdater::~NonDesktopDisplayUpdater()
#17 0x7fcb9a300df1 ash::DisplayManager::CreateMirrorWindowIfAny()

Original issue's description:
> Force calling PostDisplayConfigurationChange() even if earyling out in UpdateDisplays
>
> When changing from software mirroring mode to sinlge display mode, it
> is possible there is no need to update |displays_| and we early out
> UpdateDisplays(). But we still want to run the PostDisplayConfigurationChange()
> cause there are some clients need to act on this, e.g.
> TouchTransformerController needs to adjust the TouchTransformer when
> switching from dual displays to single display.
>
> BUG=chrome-os-partner:31868
> TEST=tested on Big, after existing software mirroring mode, the touch location
>      transformation is still correct.
>
> Committed: https://crrev.com/4802a8552a40e1f80606ca7171dc2f79930e7fb3
> Cr-Commit-Position: refs/heads/master@{#294481}

[email protected],[email protected]
NOTREECHECKS=true
NOTRY=true
BUG=chrome-os-partner:31868

Review URL: https://codereview.chromium.org/569553002

Cr-Commit-Position: refs/heads/master@{#294553}

Author: engedy

ash/display/display_controller_unittest.cc

@@ -655,8 +655,7 @@ TEST_F(DisplayControllerTest, BoundsUpdated) {
 
   // No change
   UpdateDisplay("400x500*2,300x300");
-  // We still call into Pre/PostDisplayConfigurationChange().
-  EXPECT_EQ(1, observer.CountAndReset());
+  EXPECT_EQ(0, observer.CountAndReset());
   EXPECT_EQ(0, observer.GetFocusChangedCountAndReset());
   EXPECT_EQ(0, observer.GetActivationChangedCountAndReset());
 

ash/display/display_manager.cc

@@ -884,6 +884,13 @@ void DisplayManager::UpdateDisplays(
   scoped_ptr<NonDesktopDisplayUpdater> non_desktop_display_updater(
       new NonDesktopDisplayUpdater(this, delegate_));
 
+  // Do not update |displays_| if there's nothing to be updated. Without this,
+  // it will not update the display layout, which causes the bug
+  // http://crbug.com/155948.
+  if (display_changes.empty() && added_display_indices.empty() &&
+      removed_displays.empty()) {
+    return;
+  }
   // Clear focus if the display has been removed, but don't clear focus if
   // the destkop has been moved from one display to another
   // (mirror -> docked, docked -> single internal).
@@ -893,22 +900,6 @@ void DisplayManager::UpdateDisplays(
   if (delegate_)
     delegate_->PreDisplayConfigurationChange(clear_focus);
 
-  // Do not update |displays_| if there's nothing to be updated. Without this,
-  // it will not update the display layout, which causes the bug
-  // http://crbug.com/155948.
-  if (display_changes.empty() && added_display_indices.empty() &&
-      removed_displays.empty()) {
-    // When changing from software mirroring mode to sinlge display mode, it
-    // is possible there is no need to update |displays_| and we early out
-    // here. But we still want to run the PostDisplayConfigurationChange()
-    // cause there are some clients need to act on this, e.g.
-    // TouchTransformerController needs to adjust the TouchTransformer when
-    // switching from dual displays to single display.
-    if (delegate_)
-      delegate_->PostDisplayConfigurationChange();
-    return;
-  }
-
   size_t updated_index;
   if (UpdateSecondaryDisplayBoundsForLayout(&new_displays, &updated_index) &&
       std::find(added_display_indices.begin(),