Fix a crash when typing in a exo window.

The exo is used on ChromeOS, it doesn't expect char event. The
InputMethodBridgeChromeOS should filters out char events.

BUG=None

Review-Url: https://codereview.chromium.org/2576973003
Cr-Commit-Position: refs/heads/master@{#438904}

chrome/browser/ui/views/ime_driver/input_method_bridge_chromeos.cc

@@ -39,7 +39,11 @@ void InputMethodBridge::ProcessKeyEvent(
     input_method_chromeos_->DispatchKeyEvent(
         key_event, base::MakeUnique<base::Callback<void(bool)>>(callback));
   } else {
-    callback.Run(false);
+    // On Linux (include ChromeOS), the mus emulates the WM_CHAR generation
+    // behaviour of Windows. But for ChromeOS, we don't expect those char
+    // events, so we filter them out.
+    const bool handled = true;
+    callback.Run(handled);
   }
 }