Revert "window-service: ignore requests to focus null"

This reverts commit d00fd143.

Reason for revert: Caused test flakiness https://crbug.com/871652

Original change's description:
> window-service: ignore requests to focus null
> 
> Here's my comment as to why this is ignored:
> 
>   // The client is asking to remove focus from a window. This is typically a
>   // side effect of the window becoming, or about to become, an unfocusable
>   // Window (for example, the Window is hiding). Windows becoming unfocusable is
>   // handled locally. Assume the request is for such a scenario and return
>   // false to ignore the change.
>   //
>   // To process null requests conflicts with top-level activation changes. For
>   // example, the typical sequence when a window is hidden is to first remove
>   // focus, and then hide the window. FocusController keys off window hiding to
>   // move activation. If this code where to set focus to null, FocusController
>   // would not see the window hiding (because the active window was set to null)
>   // and not automatically activate the next window.
>   //
>   // Another possibility for this code is to handle null as a signal to move
>   // focus to the active window (if there is one). I'm going with the simpler
>   // approach for now.
> 
> BUG=867654
> TEST=covered by tests
> 
> Change-Id: Iee8efd8895284acca4603ff22bde19adf16d8a7f
> Reviewed-on: https://chromium-review.googlesource.com/1164409
> Reviewed-by: Michael Wasserman <msw@chromium.org>
> Commit-Queue: Scott Violet <sky@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#581113}

TBR=sky@chromium.org,msw@chromium.org

Change-Id: I7710ea88b1dcb53d5ad299ff1295ecec31ce3f87
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 867654
Reviewed-on: https://chromium-review.googlesource.com/1164782Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581148}

ash/main.cc

@@ -6,7 +6,6 @@
 #include "ash/ash_service.h"
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
-#include "base/logging.h"
 #include "base/path_service.h"
 #include "services/service_manager/public/cpp/service_runner.h"
 #include "ui/base/material_design/material_design_controller.h"
@@ -16,7 +15,6 @@
 // This path is only hit in testing, not production. Production launches ash by
 // way of the utility process, which does not use this.
 MojoResult ServiceMain(MojoHandle service_request_handle) {
-  logging::SetLogPrefix("ash");
   // Load ash resources and strings.
   // TODO: investigate nuking ash_service_resources and use the same resources
   // that are used when AshService is launched via the utility process.

ash/shell/content/client/shell_main_delegate.cc

@@ -13,7 +13,6 @@
 #include "ash/shell/content/client/shell_content_browser_client.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
-#include "base/logging.h"
 #include "base/path_service.h"
 #include "content/public/utility/content_utility_client.h"
 #include "services/service_manager/public/cpp/service.h"
@@ -27,18 +26,15 @@ namespace shell {
 namespace {
 
 std::unique_ptr<service_manager::Service> CreateQuickLaunch() {
-  logging::SetLogPrefix("quick");
   return std::make_unique<quick_launch::QuickLaunchApplication>();
 }
 
 std::unique_ptr<service_manager::Service> CreateShortcutViewer() {
-  logging::SetLogPrefix("shortcut");
   return std::make_unique<
       keyboard_shortcut_viewer::ShortcutViewerApplication>();
 }
 
 std::unique_ptr<service_manager::Service> CreateTapVisualizer() {
-  logging::SetLogPrefix("tap");
   return std::make_unique<tap_visualizer::TapVisualizerApp>();
 }
 

services/ui/ws2/focus_handler.cc

@@ -51,25 +51,6 @@ bool FocusHandler::SetFocus(aura::Window* window) {
     return true;
   }
 
-  // The client is asking to remove focus from a window. This is typically a
-  // side effect of the window becoming, or about to become, an unfocusable
-  // Window (for example, the Window is hiding). Windows becoming unfocusable is
-  // handled locally. Assume the request is for such a scenario and return
-  // false to ignore the change.
-  //
-  // To process null requests conflicts with top-level activation changes. For
-  // example, the typical sequence when a window is hidden is to first remove
-  // focus, and then hide the window. FocusController keys off window hiding to
-  // move activation. If this code were to set focus to null, FocusController
-  // would not see the window hiding (because the active window was set to null)
-  // and not automatically activate the next window.
-  //
-  // Another possibility for this code is to handle null as a signal to move
-  // focus to the active window (if there is one). I'm going with the simpler
-  // approach for now.
-  if (!window)
-    return false;
-
   ClientChange change(window_tree_->property_change_tracker_.get(), window,
                       ClientChangeType::kFocus);
   focus_client->FocusWindow(window);

services/ui/ws2/focus_handler_unittest.cc

@@ -40,32 +40,6 @@ TEST(FocusHandlerTest, FocusTopLevel) {
   EXPECT_TRUE(top_level->HasFocus());
 }
 
-// This test simulates the typical sequence of a client closing a window:
-// SetFocus(nullptr) and then Hide().
-TEST(FocusHandlerTest, ActiveWindowChangesAfterSetFocusToNullAndHide) {
-  // Create two top-levels and focus the second.
-  WindowServiceTestSetup setup;
-  aura::Window* top_level1 =
-      setup.window_tree_test_helper()->NewTopLevelWindow();
-  ASSERT_TRUE(top_level1);
-  top_level1->Show();
-  aura::Window* top_level2 =
-      setup.window_tree_test_helper()->NewTopLevelWindow();
-  ASSERT_TRUE(top_level2);
-  top_level2->Show();
-  EXPECT_TRUE(setup.window_tree_test_helper()->SetFocus(top_level2));
-  EXPECT_TRUE(top_level2->HasFocus());
-
-  // SetFocus(nullptr) should fail (focus should not change).
-  EXPECT_FALSE(setup.window_tree_test_helper()->SetFocus(nullptr));
-  EXPECT_TRUE(top_level2->HasFocus());
-
-  // Hiding |top_level2| should focus |top_level1|.
-  top_level2->Hide();
-  EXPECT_FALSE(top_level2->HasFocus());
-  EXPECT_TRUE(top_level1->HasFocus());
-}
-
 TEST(FocusHandlerTest, FocusNull) {
   WindowServiceTestSetup setup;
   aura::Window* top_level =
@@ -74,8 +48,8 @@ TEST(FocusHandlerTest, FocusNull) {
   top_level->Show();
   EXPECT_TRUE(setup.window_tree_test_helper()->SetFocus(top_level));
   EXPECT_TRUE(top_level->HasFocus());
-  EXPECT_FALSE(setup.window_tree_test_helper()->SetFocus(nullptr));
-  EXPECT_TRUE(top_level->HasFocus());
+  EXPECT_TRUE(setup.window_tree_test_helper()->SetFocus(nullptr));
+  EXPECT_FALSE(top_level->HasFocus());
 }
 
 TEST(FocusHandlerTest, FocusChild) {