bluetooth: Move BluetoothDispatcherHost IPC handling to UI thread.

Instead of IPC handlers posting tasks to UI thread, override
BrowserMessageFilter::OverrideThreadForMessage to have all messages
delivered to UI thread.

Also, make BluetoothDispatcherHost final.

BUG=420284

Review URL: https://codereview.chromium.org/1112033002

Cr-Commit-Position: refs/heads/master@{#327584}

2 files changed, 19 insertions, 33 deletions

diff --git a/content/browser/bluetooth/bluetooth_dispatcher_host.cc b/content/browser/bluetooth/bluetooth_dispatcher_host.cc
index fb62188..c7ddbd1 100644
--- a/content/browser/bluetooth/bluetooth_dispatcher_host.cc
+++ b/content/browser/bluetooth/bluetooth_dispatcher_host.cc
@@ -32,11 +32,19 @@ scoped_refptr<BluetoothDispatcherHost> BluetoothDispatcherHost::Create() {
 }
 
 void BluetoothDispatcherHost::OnDestruct() const {
+  // See class comment: UI Thread Note.
   BrowserThread::DeleteOnUIThread::Destruct(this);
 }
 
+void BluetoothDispatcherHost::OverrideThreadForMessage(
+    const IPC::Message& message,
+    content::BrowserThread::ID* thread) {
+  // See class comment: UI Thread Note.
+  *thread = BrowserThread::UI;
+}
+
 bool BluetoothDispatcherHost::OnMessageReceived(const IPC::Message& message) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(BluetoothDispatcherHost, message)
   IPC_MESSAGE_HANDLER(BluetoothHostMsg_RequestDevice, OnRequestDevice)
@@ -72,16 +80,6 @@ void BluetoothDispatcherHost::set_adapter(
 }
 
 void BluetoothDispatcherHost::OnRequestDevice(int thread_id, int request_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  BrowserThread::PostTask(BrowserThread::UI,
-                          FROM_HERE,
-                          base::Bind(
-                              &BluetoothDispatcherHost::OnRequestDeviceOnUI,
-                              this, thread_id, request_id));
-}
-
-void BluetoothDispatcherHost::OnRequestDeviceOnUI(int thread_id,
-                                                  int request_id) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   // TODO(scheib) Extend this very simple mock implementation by using
   // device/bluetooth/test mock adapter and related classes.
@@ -148,18 +146,6 @@ void BluetoothDispatcherHost::OnConnectGATT(
     int thread_id,
     int request_id,
     const std::string& device_instance_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  BrowserThread::PostTask(BrowserThread::UI,
-                          FROM_HERE,
-                          base::Bind(
-                              &BluetoothDispatcherHost::OnConnectGATTOnUI,
-                              this, thread_id, request_id, device_instance_id));
-}
-
-void BluetoothDispatcherHost::OnConnectGATTOnUI(
-    int thread_id,
-    int request_id,
-    const std::string& device_instance_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   // TODO(ortuno): Add actual implementation of connectGATT. This needs to be
   // done after the "allowed devices map" is implemented.
@@ -169,7 +155,7 @@ void BluetoothDispatcherHost::OnConnectGATTOnUI(
 
 void BluetoothDispatcherHost::OnSetBluetoothMockDataSetForTesting(
     const std::string& name) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (name == "RejectRequestDevice_NotFoundError") {
     bluetooth_mock_data_set_ = MockData::REJECT;
     bluetooth_request_device_reject_type_ = BluetoothError::NOT_FOUND;
diff --git a/content/browser/bluetooth/bluetooth_dispatcher_host.h b/content/browser/bluetooth/bluetooth_dispatcher_host.h
index a49c759..6677f79 100644
--- a/content/browser/bluetooth/bluetooth_dispatcher_host.h
+++ b/content/browser/bluetooth/bluetooth_dispatcher_host.h
@@ -14,22 +14,25 @@ namespace content {
 
 // Dispatches and sends bluetooth related messages sent to/from a child
 // process BluetoothDispatcher from/to the main browser process.
-// Constructed on the main (UI) thread and receives IPC on the IO thread.
+//
 // Intended to be instantiated by the RenderProcessHost and installed as
 // a filter on the channel. BrowserMessageFilter is refcounted and typically
 // lives as long as it is installed on a channel.
 //
-// BluetoothDispatcherHost primarily operates on the UI thread because the
-// BluetoothAdapter and related objects live there. An exception is made for
-// Receiving IPC on the IO thread.
-class BluetoothDispatcherHost : public BrowserMessageFilter,
-                                public device::BluetoothAdapter::Observer {
+// UI Thread Note:
+// BluetoothDispatcherHost is constructed, operates, and destroyed on the UI
+// thread because BluetoothAdapter and related objects live there.
+class BluetoothDispatcherHost final
+    : public BrowserMessageFilter,
+      public device::BluetoothAdapter::Observer {
  public:
   // Creates a BluetoothDispatcherHost.
   static scoped_refptr<BluetoothDispatcherHost> Create();
 
   // BrowserMessageFilter:
   void OnDestruct() const override;
+  void OverrideThreadForMessage(const IPC::Message& message,
+                                BrowserThread::ID* thread) override;
   bool OnMessageReceived(const IPC::Message& message) override;
 
  protected:
@@ -46,11 +49,8 @@ class BluetoothDispatcherHost : public BrowserMessageFilter,
 
   // IPC Handlers, see definitions in bluetooth_messages.h.
   void OnRequestDevice(int thread_id, int request_id);
-  void OnRequestDeviceOnUI(int thread_id, int request_id);
   void OnConnectGATT(int thread_id, int request_id,
                      const std::string& device_instance_id);
-  void OnConnectGATTOnUI(int thread_id, int request_id,
-                         const std::string& device_instance_id);
   void OnSetBluetoothMockDataSetForTesting(const std::string& name);
 
   // A BluetoothAdapter instance representing an adapter of the system.