Disable stuck key detection on ChromeOS.

Since we can't rely on the modifier flags on ChromeOS, we can't use them
as a way to detect stuck modifier keys. This means that some actions
(including locking the screen) will result in Ctrl and Shift being stuck,
effectively regressing crbug.com/464534.

BUG=337509,484329

Review URL: https://codereview.chromium.org/1145863002

Cr-Commit-Position: refs/heads/master@{#330899}

remoting/client/plugin/chromoting_instance.cc

@@ -643,8 +643,8 @@ void ChromotingInstance::HandleConnect(const base::DictionaryValue& data) {
   VLOG(0) << "Connecting to " << host_jid
           << ". Local jid: " << local_jid << ".";
 
-#if defined(OS_NACL)
   std::string key_filter;
+#if defined(OS_NACL)
   if (!data.GetString("keyFilter", &key_filter)) {
     NOTREACHED();
     normalizing_input_filter_.reset(new protocol::InputFilter(&key_mapper_));
@@ -661,12 +661,19 @@ void ChromotingInstance::HandleConnect(const base::DictionaryValue& data) {
 #elif defined(OS_MACOSX)
   normalizing_input_filter_.reset(new NormalizingInputFilterMac(&key_mapper_));
 #elif defined(OS_CHROMEOS)
+  key_filter = "cros";
   normalizing_input_filter_.reset(new NormalizingInputFilterCros(&key_mapper_));
 #else
   normalizing_input_filter_.reset(new protocol::InputFilter(&key_mapper_));
 #endif
   input_handler_.set_input_stub(normalizing_input_filter_.get());
 
+  // Enable stuck modifier key detection on platforms other than ChromeOS.
+  // ChromeOS doesn't set modifier flags for "rewritten" keyboard events
+  // such as Alt+Backspace, which causes ReleaseAllIfModifiersStuck to
+  // incorrectly release all keys, so don't enable it on that platform.
+  input_handler_.set_detect_stuck_modifiers(key_filter != "cros");
+
   // PPB_VideoDecoder is not always enabled because it's broken in some versions
   // of Chrome. See crbug.com/447403 .
   bool enable_video_decode_renderer = false;

remoting/client/plugin/pepper_input_handler.cc

@@ -118,10 +118,12 @@ PepperInputHandler::PepperInputHandler(
       wheel_delta_x_(0),
       wheel_delta_y_(0),
       wheel_ticks_x_(0),
-      wheel_ticks_y_(0) {
+      wheel_ticks_y_(0),
+      detect_stuck_modifiers_(false) {
 }
 
 bool PepperInputHandler::HandleInputEvent(const pp::InputEvent& event) {
+  if (detect_stuck_modifiers_)
     ReleaseAllIfModifiersStuck(event);
 
   switch (event.GetType()) {

remoting/client/plugin/pepper_input_handler.h

@@ -40,6 +40,11 @@ class PepperInputHandler {
     send_mouse_move_deltas_ = enable;
   }
 
+  // Enable or disable detection of stuck modifier keys.
+  void set_detect_stuck_modifiers(bool detect) {
+    detect_stuck_modifiers_ = detect;
+  }
+
   // Processes PPAPI events and dispatches them to |input_stub_|.
   bool HandleInputEvent(const pp::InputEvent& event);
 
@@ -76,6 +81,9 @@ class PepperInputHandler {
   float wheel_ticks_x_;
   float wheel_ticks_y_;
 
+  // Whether or not to check for stuck modifier keys on keyboard input events.
+  bool detect_stuck_modifiers_;
+
   DISALLOW_COPY_AND_ASSIGN(PepperInputHandler);
 };