Hook up TABLET_MODE switch to maximize_mode_controller

ash/wm/maximize_mode/maximize_mode_controller.cc

Index: ash/wm/maximize_mode/maximize_mode_controller.cc
diff --git a/ash/wm/maximize_mode/maximize_mode_controller.cc b/ash/wm/maximize_mode/maximize_mode_controller.cc
index 9d8b18dae29de82390b61d4e439eca666dfd59db..f03ad8a362923daded2e741226d52a7a9c5c3f81 100644
--- a/ash/wm/maximize_mode/maximize_mode_controller.cc
+++ b/ash/wm/maximize_mode/maximize_mode_controller.cc
@@ -103,6 +103,9 @@ MaximizeModeController::MaximizeModeController()
       lid_open_past_180_(false),
       touchview_usage_interval_start_time_(base::Time::Now()),
       tick_clock_(new base::DefaultTickClock()),
+#if defined(OS_CHROMEOS)
+      force_maximize_mode_(false),
+#endif
       lid_is_closed_(false) {
   Shell* shell = Shell::GetInstance();
   shell->AddShellObserver(this);
@@ -224,6 +227,20 @@ void MaximizeModeController::LidEventReceived(bool open,
   LeaveMaximizeMode();
 }
 
+void MaximizeModeController::TabletModeEventReceived(
+    bool on,
+    const base::TimeTicks& time) {
+  if (on) {
+    force_maximize_mode_ = true;
+    EnterMaximizeMode();
+  } else {
+    force_maximize_mode_ = false;
+    // Set lid_open_past_180_ so that we get a chance to decide whether to
+    // leave maximize mode.
+    lid_open_past_180_ = true;

[jonross, 2016/06/03 03:27:19]

I think that this should be set when the tablet mode on event is received. 

Then the tablet mode early exit could be in HandleHingeRotation.

[jcliang, 2016/06/03 05:28:49]

If lid_open_past_180_ is set when the tablet mode on event is received, there
will be a race between HandleHingeRotation() and here. HandleHingeRotation()
could unset lid_open_past_180_ right after we set it here.

+  }
+}
+
 void MaximizeModeController::SuspendImminent() {
   // The system is about to suspend, so record TouchView usage interval metrics
   // based on whether TouchView mode is currently active.
@@ -332,6 +349,10 @@ void MaximizeModeController::LeaveMaximizeMode() {
     return;
   }
 
+#if defined(OS_CHROMEOS)
+  if (force_maximize_mode_)
+    return;

[jonross, 2016/06/03 03:27:19]

With this here it is possible for the tablet mode to be active, and for the
keyboard to be reenabled on line 343

[jcliang, 2016/06/03 05:28:49]

Done.

+#endif
   if (!IsMaximizeModeWindowManagerEnabled())
     return;
   EnableMaximizeModeWindowManager(false);