Fleshes out the basic set of focus rules a bit more.

ash/wm/ash_focus_rules.cc

Index: ash/wm/ash_focus_rules.cc
===================================================================
--- ash/wm/ash_focus_rules.cc	(revision 170971)
+++ ash/wm/ash_focus_rules.cc	(working copy)
@@ -4,11 +4,45 @@
 
 #include "ash/wm/ash_focus_rules.h"
 
+#include "ash/shell.h"
+#include "ash/shell_window_ids.h"
+#include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
 
 namespace ash {
 namespace wm {
+namespace {
 
+// These are the list of container ids of containers which may contain windows
+// that need to be activated in the order that they should be activated.
+const int kWindowContainerIds[] = {
+    internal::kShellWindowId_LockSystemModalContainer,
+    internal::kShellWindowId_SettingBubbleContainer,
+    internal::kShellWindowId_LockScreenContainer,
+    internal::kShellWindowId_SystemModalContainer,
+    internal::kShellWindowId_AlwaysOnTopContainer,
+    internal::kShellWindowId_AppListContainer,
+    internal::kShellWindowId_DefaultContainer,
+
+    // Panel, launcher and status are intentionally checked after other
+    // containers even though these layers are higher. The user expects their
+    // windows to be focused before these elements.
+    internal::kShellWindowId_PanelContainer,
+    internal::kShellWindowId_LauncherContainer,
+    internal::kShellWindowId_StatusContainer,
+};
+
+bool BelongsToContainerWithEqualOrGreaterId(const aura::Window* window,
+                                            int container_id) {
+  for (; window; window = window->parent()) {
+    if (window->id() >= container_id)
+      return true;
+  }
+  return false;
+}
+
+}  // namespace
+
 ////////////////////////////////////////////////////////////////////////////////
 // AshFocusRules, public:
 
@@ -21,29 +55,45 @@
 ////////////////////////////////////////////////////////////////////////////////
 // AshFocusRules, views::corewm::FocusRules:
 
-bool AshFocusRules::CanActivateWindow(aura::Window* window) {
-  return window && !!window->parent();
-}
+bool AshFocusRules::SupportsChildActivation(aura::Window* window) {
+  if (window->id() == internal::kShellWindowId_WorkspaceContainer)
+    return true;
 
-bool AshFocusRules::CanFocusWindow(aura::Window* window) {
-  aura::Window* activatable = GetActivatableWindow(window);
-  return activatable->Contains(window) && window->CanFocus();
-}
+  if (window->id() != internal::kShellWindowId_DefaultContainer)
+    return false;
 
-aura::Window* AshFocusRules::GetActivatableWindow(aura::Window* window) {
-  return window;
+  for (size_t i = 0; i < arraysize(kWindowContainerIds); i++) {
+    if (window->id() == kWindowContainerIds[i])
+      return true;
+  }
+  return false;
 }
 
-aura::Window* AshFocusRules::GetFocusableWindow(aura::Window* window) {
-  return window;
-}
+bool AshFocusRules::IsWindowConsideredVisibleForActivation(
+    aura::Window* window) {
+  if (BaseFocusRules::IsWindowConsideredVisibleForActivation(window))
+    return true;
 
-aura::Window* AshFocusRules::GetNextActivatableWindow(aura::Window* ignore) {
-  return NULL;
+  // Minimized windows are hidden in their minimized state, but they can always
+  // be activated.
+  if (wm::IsWindowMinimized(window))
+    return true;
+
+  return window->TargetVisibility() && (window->parent()->id() ==
+      internal::kShellWindowId_WorkspaceContainer || window->parent()->id() ==
+      internal::kShellWindowId_LockScreenContainer);
 }
 
-aura::Window* AshFocusRules::GetNextFocusableWindow(aura::Window* ignore) {
-  return GetFocusableWindow(ignore->parent());
+bool AshFocusRules::CanActivateWindow(aura::Window* window) {
+  if (!BaseFocusRules::CanActivateWindow(window))
+    return false;
+
+  if (Shell::GetInstance()->IsSystemModalWindowOpen()) {
+    return BelongsToContainerWithEqualOrGreaterId(
+          window, internal::kShellWindowId_SystemModalContainer);
+  }
+
+  return true;
 }
 
 }  // namespace wm