Double clicking the resize handle should expand window along that axis.

ash/wm/workspace/workspace_event_filter.cc

Index: ash/wm/workspace/workspace_event_filter.cc
===================================================================
--- ash/wm/workspace/workspace_event_filter.cc	(revision 124527)
+++ ash/wm/workspace/workspace_event_filter.cc	(working copy)
@@ -9,9 +9,13 @@
 #include "ash/wm/window_util.h"
 #include "ash/wm/workspace/workspace_layout_manager.h"
 #include "ash/wm/workspace/workspace_window_resizer.h"
+#include "ui/aura/client/aura_constants.h"
 #include "ui/aura/event.h"
+#include "ui/aura/screen_aura.h"
 #include "ui/aura/window.h"
+#include "ui/aura/window_delegate.h"
 #include "ui/base/hit_test.h"
+#include "ui/gfx/compositor/scoped_layer_animation_settings.h"
 
 namespace {
 
@@ -26,6 +30,19 @@
   window_frame->OnWindowHoverChanged(hovered);
 }
 
+void SingleAxisMaximize(aura::Window* window, const gfx::Rect& maximize_rect) {
+  window->ClearProperty(aura::client::kRestoreBoundsKey);
+  window->SetProperty(aura::client::kRestoreBoundsKey,
+                      new gfx::Rect(window->bounds()));
+  window->SetBounds(maximize_rect);
+}
+
+void SingleAxisUnmaximize(aura::Window* window,
+                          const gfx::Rect& restore_bounds) {
+  window->SetBounds(restore_bounds);
+  window->ClearProperty(aura::client::kRestoreBoundsKey);
+}
+
 }  // namespace
 
 namespace ash {
@@ -51,6 +68,9 @@
     case ui::ET_MOUSE_EXITED:
       UpdateHoveredWindow(NULL);
       break;
+    case ui::ET_MOUSE_PRESSED:
+      HandleVerticalResizeDoubleClick(target, event);
+      break;
     default:
       break;
   }
@@ -90,5 +110,43 @@
     hovered_window_->AddObserver(this);
 }
 
+void WorkspaceEventFilter::HandleVerticalResizeDoubleClick(
+    aura::Window* target,
+    aura::MouseEvent* event) {
+  if (event->flags() & ui::EF_IS_DOUBLE_CLICK) {
+    int component =
+        target->delegate()->GetNonClientComponent(event->location());
+    gfx::Rect work_area =
+        gfx::Screen::GetMonitorWorkAreaNearestWindow(target);
+    const gfx::Rect* restore_bounds =
+        target->GetProperty(aura::client::kRestoreBoundsKey);
+    if (component == HTBOTTOM || component == HTTOP) {
+      if (restore_bounds &&
+          (target->bounds().height() == work_area.height() &&
+           target->bounds().y() == work_area.y())) {
+        SingleAxisUnmaximize(target, *restore_bounds);
+      } else {
+        SingleAxisMaximize(target,
+                           gfx::Rect(target->bounds().x(),
+                                     work_area.y(),
+                                     target->bounds().width(),
+                                     work_area.height()));
+      }
+    } else if (component == HTLEFT || component == HTRIGHT) {
+      if (restore_bounds &&
+          (target->bounds().width() == work_area.width() &&
+           target->bounds().x() == work_area.x())) {
+        SingleAxisUnmaximize(target, *restore_bounds);
+      } else {
+        SingleAxisMaximize(target,
+                           gfx::Rect(work_area.x(),
+                                     target->bounds().y(),
+                                     work_area.width(),
+                                     target->bounds().height()));
+      }
+    }
+  }
+}
+
 }  // namespace internal
 }  // namespace ash