[Fuchsia] Rewrite MessagePumpFuchsia based on AsyncDispatcher

Now MessagePumpFuchsia runs AsyncDispatcher to handle IO events. This will
allow to use async lib and libraries that depend on it (such as FIDL) on
UI and IO threads.

Bug: 831384
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I981d18f9e07d25a5cd4f6006714af91557c0c795
Reviewed-on: https://chromium-review.googlesource.com/985648
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551399}

base/message_loop/message_pump_fuchsia.h

@@ -5,17 +5,18 @@
 #ifndef BASE_MESSAGE_LOOP_MESSAGE_PUMP_FUCHSIA_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_FUCHSIA_H_
 
+#include <fdio/io.h>
+#include <lib/async/wait.h>
+
 #include "base/base_export.h"
-#include "base/fuchsia/scoped_zx_handle.h"
+#include "base/fuchsia/async_dispatcher.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_pump.h"
 #include "base/message_loop/watchable_io_message_pump_posix.h"
 
-#include <fdio/io.h>
-#include <fdio/private.h>
-#include <zircon/syscalls/port.h>
+typedef struct fdio fdio_t;
 
 namespace base {
 
@@ -33,7 +34,7 @@ class BASE_EXPORT MessagePumpFuchsia : public MessagePump,
   };
 
   // Manages an active watch on an zx_handle_t.
-  class ZxHandleWatchController {
+  class ZxHandleWatchController : public async_wait_t {
    public:
     explicit ZxHandleWatchController(const Location& from_here);
     // Deleting the Controller implicitly calls StopWatchingZxHandle.
@@ -46,6 +47,17 @@ class BASE_EXPORT MessagePumpFuchsia : public MessagePump,
     const Location& created_from_location() { return created_from_location_; }
 
    protected:
+    friend class MessagePumpFuchsia;
+
+    virtual bool WaitBegin();
+
+    static void HandleSignal(async_t* async,
+                             async_wait_t* wait,
+                             zx_status_t status,
+                             const zx_packet_signal_t* signal);
+
+    const Location created_from_location_;
+
     // This bool is used by the pump when invoking the ZxHandleWatcher callback,
     // and by the FdHandleWatchController when invoking read & write callbacks,
     // to cope with the possibility of the caller deleting the *Watcher within
@@ -54,28 +66,8 @@ class BASE_EXPORT MessagePumpFuchsia : public MessagePump,
     // to check the value on the stack to short-cut any post-callback work.
     bool* was_stopped_ = nullptr;
 
-   protected:
-    friend class MessagePumpFuchsia;
-
-    // Start watching the handle.
-    virtual bool WaitBegin();
-
-    // Called by MessagePumpFuchsia when the handle is signalled. Accepts the
-    // set of signals that fired, and returns the intersection with those the
-    // caller is interested in.
-    zx_signals_t WaitEnd(zx_signals_t observed);
-
-    // Returns the key to use to uniquely identify this object's wait operation.
-    uint64_t wait_key() const {
-      return static_cast<uint64_t>(reinterpret_cast<uintptr_t>(this));
-    }
-
-    const Location created_from_location_;
-
     // Set directly from the inputs to WatchFileDescriptor.
     ZxHandleWatcher* watcher_ = nullptr;
-    zx_handle_t handle_ = ZX_HANDLE_INVALID;
-    zx_signals_t desired_signals_ = 0;
 
     // Used to safely access resources owned by the associated message pump.
     WeakPtr<MessagePumpFuchsia> weak_pump_;
@@ -84,10 +76,6 @@ class BASE_EXPORT MessagePumpFuchsia : public MessagePump,
     // after triggering.
     bool persistent_ = false;
 
-    // Used to determine whether an asynchronous wait operation is active on
-    // this controller.
-    bool has_begun_ = false;
-
     DISALLOW_COPY_AND_ASSIGN(ZxHandleWatchController);
   };
 
@@ -148,14 +136,14 @@ class BASE_EXPORT MessagePumpFuchsia : public MessagePump,
   void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
 
  private:
-  // Handles IO events from the |port_|. Returns true if any events were
-  // received.
+  // Handles IO events by running |async_dispatcher_|. Returns true if any
+  // events were received or if ScheduleWork() was called.
   bool HandleEvents(zx_time_t deadline);
 
   // This flag is set to false when Run should return.
   bool keep_running_ = true;
 
-  ScopedZxHandle port_;
+  AsyncDispatcher async_dispatcher_;
 
   // The time at which we should call DoDelayedWork.
   TimeTicks delayed_work_time_;