[gamepad] Fix Joy-Con Charging Grip disconnection crash

This CL avoids a crash when disconnecting a Joy-Con Charging
Grip gamepad. The Joy-Con Charging Grip is a USB-C device that
docks with two Nintendo Switch Joy-Cons and allows them to
behave like a single USB gamepad.

When disconnecting, NintendoDataFetcher::RemoveDevice decomposes
the gamepad representing the charging grip into its Joy-Con
subcomponents (composite_left_ and composite_right_). The parent
device is then shut down, which may trigger a "stop vibration"
command. This causes a null dereference when it tries to forward
the vibration command to the subcomponent.

To fix, the vibration command is sent before the subcomponents
have been removed from the parent device and additional checks
are added to ensure the subcomponents are not dereferenced after
the parent is decomposed.

BUG=995548

Change-Id: I1d82e423b134ab3c99dd1e98a6615555cfadd47e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1758980Reviewed-by: Ovidio de Jesús Ruiz-Henríquez <odejesush@chromium.org>
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691885}

device/gamepad/nintendo_controller.cc

@@ -886,6 +886,9 @@ bool NintendoController::IsNintendoController(uint16_t vendor_id,
 
 std::vector<std::unique_ptr<NintendoController>>
 NintendoController::Decompose() {
+  // Stop any ongoing vibration effects before decomposing the device.
+  SetZeroVibration();
+
   std::vector<std::unique_ptr<NintendoController>> decomposed_devices;
   if (composite_left_)
     decomposed_devices.push_back(std::move(composite_left_));
@@ -951,7 +954,7 @@ bool NintendoController::IsUsable() const {
   if (state_ != kInitialized)
     return false;
   if (is_composite_)
-    return true;
+    return composite_left_ && composite_right_;
   switch (gamepad_id_) {
     case GamepadId::kNintendoProduct2009:
     case GamepadId::kNintendoProduct2006:
@@ -968,10 +971,12 @@ bool NintendoController::IsUsable() const {
 }
 
 bool NintendoController::HasGuid(const std::string& guid) const {
-  if (is_composite_)
+  if (is_composite_) {
+    DCHECK(composite_left_);
+    DCHECK(composite_right_);
     return composite_left_->HasGuid(guid) || composite_right_->HasGuid(guid);
-  else
-    return device_info_->guid == guid;
+  }
+  return device_info_->guid == guid;
 }
 
 GamepadStandardMappingFunction NintendoController::GetMappingFunction() const {
@@ -1027,6 +1032,8 @@ void NintendoController::UpdatePadConnected() {
 
 void NintendoController::UpdateGamepadState(Gamepad& pad) const {
   if (is_composite_) {
+    DCHECK(composite_left_);
+    DCHECK(composite_right_);
     // If this is a composite device, update the gamepad state using the state
     // of the subcomponents.
     pad.connected = true;
@@ -1709,8 +1716,10 @@ void NintendoController::SetVibration(double strong_magnitude,
                                       double weak_magnitude) {
   if (is_composite_) {
     // Split the vibration effect between the left and right subdevices.
-    composite_left_->SetVibration(strong_magnitude, 0);
-    composite_right_->SetVibration(0, weak_magnitude);
+    if (composite_left_ && composite_right_) {
+      composite_left_->SetVibration(strong_magnitude, 0);
+      composite_right_->SetVibration(0, weak_magnitude);
+    }
   } else {
     RequestVibration(kVibrationFrequencyStrongRumble,
                      kVibrationAmplitudeStrongRumbleMax * strong_magnitude,