Reworks the workspace code. Here's the new heuristics:

ash/wm/workspace/workspace_manager.cc

Index: ash/wm/workspace/workspace_manager.cc
diff --git a/ash/wm/workspace/workspace_manager.cc b/ash/wm/workspace/workspace_manager.cc
index a9884b3bf677c118f7639ea47af8e94e1506b52f..9fc41e9d0a2629aa154d5d748f6f39ac09728b2b 100644
--- a/ash/wm/workspace/workspace_manager.cc
+++ b/ash/wm/workspace/workspace_manager.cc
@@ -6,14 +6,17 @@
 
 #include <algorithm>
 
+#include "ash/wm/property_util.h"
+#include "ash/wm/window_util.h"
 #include "ash/wm/workspace/workspace.h"
-#include "ash/wm/workspace/workspace_observer.h"
 #include "base/auto_reset.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
+#include "ui/aura/client/aura_constants.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/screen_aura.h"
 #include "ui/aura/window.h"
+#include "ui/base/ui_base_types.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/compositor/layer_animator.h"
 #include "ui/gfx/compositor/scoped_layer_animation_settings.h"
@@ -29,6 +32,20 @@ const int kWorkspaceHorizontalMargin = 50;
 const float kMaxOverviewScale = 0.9f;
 const float kMinOverviewScale = 0.3f;
 
+// Sets the visibility of the layer of each window in |windows| to |value|. We
+// set the visibility of the layer rather than the Window so that views doesn't
+// see the visibility change.
+// TODO: revisit this. Ideally the Window would think it's still visibile after
+// this. May be possible after Ben lands his changes.
+void SetWindowLayerVisibility(const std::vector<aura::Window*>& windows,
+                              bool value) {
+  for (size_t i = 0; i < windows.size(); ++i){
+    if (windows[i]->layer())
+      windows[i]->layer()->SetVisible(value);
+    SetWindowLayerVisibility(windows[i]->transient_children(), value);
+  }
+}
+
 }
 
 namespace ash {
@@ -43,161 +60,156 @@ WorkspaceManager::WorkspaceManager(aura::Window* contents_view)
       workspace_size_(
           gfx::Screen::GetMonitorAreaNearestWindow(contents_view_).size()),
       is_overview_(false),
-      layout_in_progress_(false),
       ignored_window_(NULL) {
   DCHECK(contents_view);
 }
 
 WorkspaceManager::~WorkspaceManager() {
+  for (size_t i = 0; i < workspaces_.size(); ++i) {
+    Workspace* workspace = workspaces_[i];
+    for (size_t j = 0; j < workspace->windows().size(); ++j)
+      workspace->windows()[j]->RemoveObserver(this);
+  }
   std::vector<Workspace*> copy_to_delete(workspaces_);
   STLDeleteElements(&copy_to_delete);
 }
 
-Workspace* WorkspaceManager::CreateWorkspace() {
-  Workspace* workspace = new Workspace(this);
-  LayoutWorkspaces();
-  return workspace;
+bool WorkspaceManager::IsManagedWindow(aura::Window* window) const {
+  return window->type() == aura::client::WINDOW_TYPE_NORMAL &&
+         !window->transient_parent();
 }
 
-Workspace* WorkspaceManager::GetActiveWorkspace() const {
-  return active_workspace_;
-}
+void WorkspaceManager::AddWindow(aura::Window* window) {
+  DCHECK(IsManagedWindow(window));
 
-Workspace* WorkspaceManager::FindBy(aura::Window* window) const {
-  int index = GetWorkspaceIndexContaining(window);
-  return index < 0 ? NULL : workspaces_[index];
-}
+  if (FindBy(window))
+    return;  // Already know about this window.
 
-aura::Window* WorkspaceManager::FindRotateWindowForLocation(
-    const gfx::Point& point) {
-  for (Workspaces::const_iterator i = workspaces_.begin();
-       i != workspaces_.end();
-       ++i) {
-    aura::Window* window = (*i)->FindRotateWindowForLocation(point);
-    if (window)
-      return window;
+  window->AddObserver(this);
+
+  if (!window->GetProperty(aura::client::kShowStateKey)) {
+    // TODO: set maximized if width < x.
+    window->SetIntProperty(aura::client::kShowStateKey, ui::SHOW_STATE_NORMAL);
   }
-  return NULL;
-}
 
-void WorkspaceManager::LayoutWorkspaces() {
-  UpdateContentsView();
+  // TODO: handle fullscreen.
+  if (window_util::IsWindowMaximized(window)) {
+    if (!GetRestoreBounds(window))
+      SetRestoreBounds(window, window->GetTargetBounds());
+    else
+      SetWindowBounds(window, GetWorkAreaBounds());
+  }
 
-  gfx::Rect bounds(workspace_size_);
-  int x = 0;
-  for (Workspaces::const_iterator i = workspaces_.begin();
-       i != workspaces_.end();
-       ++i) {
-    Workspace* workspace = *i;
-    bounds.set_x(x);
-    workspace->SetBounds(bounds);
-    x += bounds.width() + kWorkspaceHorizontalMargin;
+  Workspace* workspace = NULL;
+  Workspace::Type type_for_window = Workspace::TypeForWindow(window);
+  switch (type_for_window) {
+    case Workspace::TYPE_SPLIT:
+      // Splits either go in current workspace (if maximized or split). If the
+      // current workspace isn't split/maximized, then create a maximized
+      // workspace.
+      workspace = GetActiveWorkspace();
+      if (workspace &&
+          (workspace->type() == Workspace::TYPE_SPLIT ||
+           workspace->type() == Workspace::TYPE_MAXIMIZED)) {
+        // TODO: this needs to reset bounds of any existing windows in
+        // workspace.
+        workspace->SetType(Workspace::TYPE_SPLIT);
+      } else {
+        type_for_window = Workspace::TYPE_MAXIMIZED;
+        workspace = NULL;
+      }
+      break;
+
+    case Workspace::TYPE_NORMAL:
+      // All normal windows go in the same workspace.
+      workspace = GetNormalWorkspace();
+      break;
+
+    case Workspace::TYPE_MAXIMIZED:
+      // All maximized windows go in their own workspace.
+      break;
+
+    default:
+      NOTREACHED();
+      break;
   }
-}
 
-gfx::Rect WorkspaceManager::GetDragAreaBounds() {
-  return GetWorkAreaBounds(gfx::Rect(contents_view_->bounds().size()));
+  if (!workspace) {
+    workspace = new Workspace(this);
+    workspace->SetType(type_for_window);
+  }
+  workspace->AddWindowAfter(window, NULL);
+  workspace->Activate();
 }
 
-void WorkspaceManager::SetOverview(bool overview) {
-  if (is_overview_ == overview)
+void WorkspaceManager::RemoveWindow(aura::Window* window) {
+  Workspace* workspace = FindBy(window);
+  if (!workspace)
     return;
-  is_overview_ = overview;
-
-  ui::Transform transform;
-  if (is_overview_) {
-    // TODO(oshima|sky): We limit the how small windows can be shrinked
-    // in overview mode, thus part of the contents_view may not be visible.
-    // We need to add capability to scroll/move contents_view in overview mode.
-    float scale = std::min(
-        kMaxOverviewScale,
-        workspace_size_.width() /
-        static_cast<float>(contents_view_->bounds().width()));
-    scale = std::max(kMinOverviewScale, scale);
-
-    transform.SetScale(scale, scale);
-
-    int overview_width = contents_view_->bounds().width() * scale;
-    int dx = 0;
-    if (overview_width < workspace_size_.width()) {
-      dx = (workspace_size_.width() - overview_width) / 2;
-    } else if (active_workspace_) {
-      // Center the active workspace.
-      int active_workspace_mid_x = (active_workspace_->bounds().x() +
-          active_workspace_->bounds().width() / 2) * scale;
-      dx = workspace_size_.width() / 2 - active_workspace_mid_x;
-      dx = std::min(0, std::max(dx, workspace_size_.width() - overview_width));
-    }
+  window->RemoveObserver(this);
+  workspace->RemoveWindow(window);
+  if (workspace->is_empty())
+    delete workspace;
+}
 
-    transform.SetTranslateX(dx);
-    transform.SetTranslateY(workspace_size_.height() *  (1.0f - scale) / 2);
-  } else if (active_workspace_) {
-    transform.SetTranslateX(-active_workspace_->bounds().x());
-  }
+void WorkspaceManager::SetActiveWorkspaceByWindow(aura::Window* window) {
+  Workspace* workspace = FindBy(window);
+  if (workspace)
+    workspace->Activate();
+}
 
-  ui::ScopedLayerAnimationSettings settings(
-      contents_view_->layer()->GetAnimator());
-  contents_view_->layer()->SetTransform(transform);
+gfx::Rect WorkspaceManager::GetDragAreaBounds() {
+  return GetWorkAreaBounds();
 }
 
-void WorkspaceManager::RotateWindows(aura::Window* source,
-                                     aura::Window* target) {
-  DCHECK(source);
-  DCHECK(target);
-  int source_ws_index = GetWorkspaceIndexContaining(source);
-  int target_ws_index = GetWorkspaceIndexContaining(target);
-  DCHECK(source_ws_index >= 0);
-  DCHECK(target_ws_index >= 0);
-  if (source_ws_index == target_ws_index) {
-    workspaces_[source_ws_index]->RotateWindows(source, target);
-  } else {
-    aura::Window* insert = source;
-    aura::Window* target_to_insert = target;
-    if (source_ws_index < target_ws_index) {
-      for (int i = target_ws_index; i >= source_ws_index; --i) {
-        insert = workspaces_[i]->ShiftWindows(
-            insert, source, target_to_insert, Workspace::SHIFT_TO_LEFT);
-        // |target| can only be in the 1st workspace.
-        target_to_insert = NULL;
-      }
-    } else {
-      for (int i = target_ws_index; i <= source_ws_index; ++i) {
-        insert = workspaces_[i]->ShiftWindows(
-            insert, source, target_to_insert, Workspace::SHIFT_TO_RIGHT);
-        // |target| can only be in the 1st workspace.
-        target_to_insert = NULL;
-      }
-    }
-  }
-  FOR_EACH_OBSERVER(WorkspaceObserver, observers_,
-                    WindowMoved(this, source, target));
-  workspaces_[target_ws_index]->Activate();
+void WorkspaceManager::SetOverview(bool overview) {
+  if (is_overview_ == overview)
+    return;
+  NOTIMPLEMENTED();
 }
 
 void WorkspaceManager::SetWorkspaceSize(const gfx::Size& workspace_size) {
   if (workspace_size == workspace_size_)
     return;
   workspace_size_ = workspace_size;
-  LayoutWorkspaces();
+  for (Workspaces::const_iterator i = workspaces_.begin();
+       i != workspaces_.end(); ++i) {
+    (*i)->WorkspaceSizeChanged();
+  }
 }
 
-void WorkspaceManager::AddObserver(WorkspaceObserver* observer) {
-  observers_.AddObserver(observer);
-}
+void WorkspaceManager::OnWindowPropertyChanged(aura::Window* window,
+                                               const char* name,
+                                               void* old) {
+  if (!IsManagedWindow(window))
+    return;
 
-void WorkspaceManager::RemoveObserver(WorkspaceObserver* observer) {
-  observers_.RemoveObserver(observer);
+  if (name != aura::client::kShowStateKey)
+    return;
+  // TODO: handle fullscreen.
+  bool is_maximized = window->GetIntProperty(name) == ui::SHOW_STATE_MAXIMIZED;
+  bool was_maximized =
+      (old == reinterpret_cast<void*>(ui::SHOW_STATE_MAXIMIZED));
+  if (is_maximized == was_maximized)
+    return;
+
+  MaximizedStateChanged(window);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WorkspaceManager, private:
 
 void WorkspaceManager::AddWorkspace(Workspace* workspace) {
-  Workspaces::iterator i = std::find(workspaces_.begin(),
-                                     workspaces_.end(),
-                                     workspace);
-  DCHECK(i == workspaces_.end());
-  workspaces_.push_back(workspace);
+  DCHECK(std::find(workspaces_.begin(), workspaces_.end(),
+                   workspace) == workspaces_.end());
+  if (active_workspace_) {
+    // New workspaces go right after current workspace.
+    Workspaces::iterator i = std::find(workspaces_.begin(), workspaces_.end(),
+                                       active_workspace_);
+    workspaces_.insert(++i, workspace);
+  } else {
+    workspaces_.push_back(workspace);
+  }
 }
 
 void WorkspaceManager::RemoveWorkspace(Workspace* workspace) {
@@ -205,19 +217,25 @@ void WorkspaceManager::RemoveWorkspace(Workspace* workspace) {
                                      workspaces_.end(),
                                      workspace);
   DCHECK(i != workspaces_.end());
-  Workspace* old = NULL;
-
-  if (workspace == active_workspace_) {
-    old = active_workspace_;
-    active_workspace_ = NULL;
+  i = workspaces_.erase(i);
+  if (active_workspace_ == workspace) {
+    // TODO: need mru order.
+    if (i != workspaces_.end())
+      SetActiveWorkspace(*i);
+    else if (!workspaces_.empty())
+      SetActiveWorkspace(workspaces_.back());
+    else
+      active_workspace_ = NULL;
   }
-  workspaces_.erase(i);
-  LayoutWorkspaces();
+}
 
-  if (old) {
-    FOR_EACH_OBSERVER(WorkspaceObserver, observers_,
-                      ActiveWorkspaceChanged(this, old));
-  }
+Workspace* WorkspaceManager::GetActiveWorkspace() const {
+  return active_workspace_;
+}
+
+Workspace* WorkspaceManager::FindBy(aura::Window* window) const {
+  int index = GetWorkspaceIndexContaining(window);
+  return index < 0 ? NULL : workspaces_[index];
 }
 
 void WorkspaceManager::SetActiveWorkspace(Workspace* workspace) {
@@ -225,19 +243,17 @@ void WorkspaceManager::SetActiveWorkspace(Workspace* workspace) {
     return;
   DCHECK(std::find(workspaces_.begin(), workspaces_.end(),
                    workspace) != workspaces_.end());
-  Workspace* old = active_workspace_;
+  if (active_workspace_)
+    SetWindowLayerVisibility(active_workspace_->windows(), false);
   active_workspace_ = workspace;
+  if (active_workspace_)
+    SetWindowLayerVisibility(active_workspace_->windows(), true);
 
   is_overview_ = false;
-  UpdateContentsView();
-
-  FOR_EACH_OBSERVER(WorkspaceObserver, observers_,
-                    ActiveWorkspaceChanged(this, old));
 }
 
-gfx::Rect WorkspaceManager::GetWorkAreaBounds(
-    const gfx::Rect& workspace_bounds) {
-  gfx::Rect bounds = workspace_bounds;
+gfx::Rect WorkspaceManager::GetWorkAreaBounds() {
+  gfx::Rect bounds(workspace_size_);
   bounds.Inset(
       aura::RootWindow::GetInstance()->screen()->work_area_insets());
   return bounds;
@@ -254,23 +270,75 @@ int WorkspaceManager::GetWorkspaceIndexContaining(aura::Window* window) const {
   return -1;
 }
 
-void WorkspaceManager::UpdateContentsView() {
-  int num_workspaces = std::max(1, static_cast<int>(workspaces_.size()));
-  int total_width = workspace_size_.width() * num_workspaces +
-      kWorkspaceHorizontalMargin * (num_workspaces - 1);
-  gfx::Rect bounds(0, 0, total_width, workspace_size_.height());
+void WorkspaceManager::SetWindowBounds(aura::Window* window,
+                                       const gfx::Rect& bounds) {
+  // TODO: I suspect it's possible for this to be invoked when ignored_window_
+  // is non-NULL.
+  ignored_window_ = window;
+  window->SetBounds(bounds);
+  ignored_window_ = NULL;
+}
 
-  if (contents_view_->GetTargetBounds() != bounds)
-    contents_view_->SetBounds(bounds);
+void WorkspaceManager::SetWindowBoundsFromRestoreBounds(aura::Window* window) {
+  Workspace* workspace = FindBy(window);
+  DCHECK(workspace);
+  const gfx::Rect* restore = GetRestoreBounds(window);
+  if (restore) {
+    SetWindowBounds(window,
+                    restore->AdjustToFit(workspace->GetWorkAreaBounds()));
+  } else {
+    SetWindowBounds(window, window->bounds().AdjustToFit(
+                        workspace->GetWorkAreaBounds()));
+  }
+  ash::ClearRestoreBounds(window);
+}
 
-  // Move to active workspace.
-  if (active_workspace_) {
-    ui::Transform transform;
-    transform.SetTranslateX(-active_workspace_->bounds().x());
-    ui::ScopedLayerAnimationSettings settings(
-        contents_view_->layer()->GetAnimator());
-    contents_view_->SetTransform(transform);
+void WorkspaceManager::MaximizedStateChanged(aura::Window* window) {
+  DCHECK(IsManagedWindow(window));
+  bool is_maximized = window_util::IsWindowMaximized(window);
+  Workspace* current_workspace = FindBy(window);
+  DCHECK(current_workspace);
+  if (is_maximized) {
+    // Unmaximized -> maximized; create a new workspace (unless current only has
+    // one window).
+    SetRestoreBounds(window, window->GetTargetBounds());
+    if (current_workspace->num_windows() != 1) {
+      current_workspace->RemoveWindow(window);
+      Workspace* workspace = new Workspace(this);
+      workspace->SetType(Workspace::TYPE_MAXIMIZED);
+      workspace->AddWindowAfter(window, NULL);
+      current_workspace = workspace;
+    } else {
+      current_workspace->SetType(Workspace::TYPE_MAXIMIZED);
+    }
+    SetWindowBounds(window, GetWorkAreaBounds());
+  } else {
+    // Maximized -> unmaximized; move window to unmaximized workspace (or reuse
+    // current if there isn't one).
+    window_util::SetOpenWindowSplit(window, false);
+    Workspace* workspace = GetNormalWorkspace();
+    if (workspace) {
+      current_workspace->RemoveWindow(window);
+      DCHECK(current_workspace->is_empty());
+      workspace->AddWindowAfter(window, NULL);
+      delete current_workspace;
+      current_workspace = workspace;
+    } else {
+      current_workspace->SetType(Workspace::TYPE_NORMAL);
+    }
+
+    SetWindowBoundsFromRestoreBounds(window);
   }
+
+  SetActiveWorkspace(current_workspace);
+}
+
+Workspace* WorkspaceManager::GetNormalWorkspace() {
+  for (size_t i = 0; i < workspaces_.size(); ++i) {
+    if (workspaces_[i]->type() == Workspace::TYPE_NORMAL)
+      return workspaces_[i];
+  }
+  return NULL;
 }
 
 }  // namespace internal