Make BinderWatcher use brillo::MessageLoop.

This patch breaks the dependency between the BinderWatcher and the
base::MessageLoopForIO implementation, making it use the
brillo::MessageLoop class instead.

Bug: 26356682
TEST=Binder based `update_engine_client` still works.

Change-Id: I46a8a9c8d00d536c2d54889017f109c581eb0bc7

1 files changed, 40 insertions, 16 deletions

diff --git a/brillo/binder_watcher.cc b/brillo/binder_watcher.cc
index 32ab101..9752204 100644
--- a/brillo/binder_watcher.cc
+++ b/brillo/binder_watcher.cc
@@ -16,6 +16,7 @@
 
 #include <brillo/binder_watcher.h>
 
+#include <base/bind.h>
 #include <base/logging.h>
 #include <binder/IPCThreadState.h>
 #include <binder/ProcessState.h>
@@ -23,36 +24,59 @@
 using android::IPCThreadState;
 using android::ProcessState;
 
+namespace {
+// Called from the message loop whenever the binder file descriptor is ready.
+void OnBinderReadReady() {
+  IPCThreadState::self()->handlePolledCommands();
+}
+}  // namespace
+
 namespace brillo {
 
-BinderWatcher::BinderWatcher() = default;
+BinderWatcher::BinderWatcher(MessageLoop* message_loop)
+    : message_loop_(message_loop) {}
+
+BinderWatcher::BinderWatcher() : message_loop_(nullptr) {}
 
-BinderWatcher::~BinderWatcher() = default;
+BinderWatcher::~BinderWatcher() {
+  if (task_id_ != MessageLoop::kTaskIdNull)
+    message_loop_->CancelTask(task_id_);
+}
 
 bool BinderWatcher::Init() {
+  if (!message_loop_)
+    message_loop_ = MessageLoop::current();
+  if (!message_loop_) {
+    LOG(ERROR) << "Must initialize a brillo::MessageLoop to use BinderWatcher";
+    return false;
+  }
+
   int binder_fd = -1;
   ProcessState::self()->setThreadPoolMaxThreadCount(0);
   IPCThreadState::self()->disableBackgroundScheduling(true);
-  IPCThreadState::self()->setupPolling(&binder_fd);
-  LOG(INFO) << "Got binder FD " << binder_fd;
-  if (binder_fd < 0)
+  int err = IPCThreadState::self()->setupPolling(&binder_fd);
+  if (err != 0) {
+    LOG(ERROR) << "Error setting up binder polling: "
+               << logging::SystemErrorCodeToString(err);
     return false;
+  }
+  if (binder_fd < 0) {
+    LOG(ERROR) << "Invalid binder FD " << binder_fd;
+    return false;
+  }
+  VLOG(1) << "Got binder FD " << binder_fd;
 
-  if (!base::MessageLoopForIO::current()->WatchFileDescriptor(
-          binder_fd, true /* persistent */, base::MessageLoopForIO::WATCH_READ,
-          &watcher_, this)) {
+  task_id_ = message_loop_->WatchFileDescriptor(
+      FROM_HERE,
+      binder_fd,
+      MessageLoop::kWatchRead,
+      true /* persistent */,
+      base::Bind(&OnBinderReadReady));
+  if (task_id_ == MessageLoop::kTaskIdNull) {
     LOG(ERROR) << "Failed to watch binder FD";
     return false;
   }
   return true;
 }
 
-void BinderWatcher::OnFileCanReadWithoutBlocking(int /* fd */) {
-  IPCThreadState::self()->handlePolledCommands();
-}
-
-void BinderWatcher::OnFileCanWriteWithoutBlocking(int fd) {
-  NOTREACHED() << "Unexpected writable notification for FD " << fd;
-}
-
 }  // namespace brillo