Mark the key repeat events as handled in exo::Keyboard::OnKeyEvent().

Clients of exo expects to handle the key repeat in the client side
according to crrev.com/c/1079768.
Therefore, exo::Keyboard silently ignores the key repeat events.
However, it doesn't mark the key repeat events as handled and
they are used to invoke the accelerators.
This CL changes exo::Keyboard to mark the key repeat events as handled,
then they are not used to invoke the accelerators anymore.

Bug: b/149477038
Test: Hold Ctrl and W on an ARC++ app which eats Ctrl-W key event, and
check that the app doesn't close.

Change-Id: Iab480b94b98ea8d3e12ce67b810162f1f671e3b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2091328Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Yuichiro Hanada <yhanada@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748134}

components/exo/keyboard.cc

@@ -243,10 +243,6 @@ void Keyboard::OnKeyEvent(ui::KeyEvent* event) {
   if (!focus_)
     return;
 
-  // Ignore synthetic key repeat events.
-  if (event->is_repeat())
-    return;
-
   // If the event target is not an exo::Surface, let another handler process the
   // event. This check may not be necessary once https://crbug.com/624168 is
   // resolved.
@@ -255,6 +251,16 @@ void Keyboard::OnKeyEvent(ui::KeyEvent* event) {
     return;
   }
 
+  // Ignore synthetic key repeat events.
+  if (event->is_repeat()) {
+    // Clients should not see key repeat events and instead handle them on the
+    // client side.
+    // Mark the key repeat events as handled to avoid them from invoking
+    // accelerators.
+    event->SetHandled();
+    return;
+  }
+
   TRACE_EXO_INPUT_EVENT(event);
 
   // Process reserved accelerators before sending it to client.