Refactored gamepad polling to support dynamic sources

device/gamepad/gamepad_platform_data_fetcher_linux.cc

Index: device/gamepad/gamepad_platform_data_fetcher_linux.cc
diff --git a/device/gamepad/gamepad_platform_data_fetcher_linux.cc b/device/gamepad/gamepad_platform_data_fetcher_linux.cc
index 4781a8f7fac8b800709fc2922e2e45628691ee98..5fe3e43f848933fdddb26d152642fd939cc461b4 100644
--- a/device/gamepad/gamepad_platform_data_fetcher_linux.cc
+++ b/device/gamepad/gamepad_platform_data_fetcher_linux.cc
@@ -11,8 +11,6 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#include "base/macros.h"
-#include "base/message_loop/message_loop.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -70,13 +68,21 @@ using blink::WebGamepad;
 using blink::WebGamepads;
 
 GamepadPlatformDataFetcherLinux::GamepadPlatformDataFetcherLinux() {
-  for (size_t i = 0; i < arraysize(pad_state_); ++i) {
+  for (size_t i = 0; i < arraysize(device_fd_); ++i) {
     device_fd_[i] = -1;
-    pad_state_[i].mapper = 0;
-    pad_state_[i].axis_mask = 0;
-    pad_state_[i].button_mask = 0;
   }
+}
 
+GamepadPlatformDataFetcherLinux::~GamepadPlatformDataFetcherLinux() {
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i)
+    CloseFileDescriptorIfValid(device_fd_[i]);
+}
+
+GamepadSource GamepadPlatformDataFetcherLinux::source() {
+  return Factory::static_source();
+}
+
+void GamepadPlatformDataFetcherLinux::OnAddedToProvider() {
   std::vector<UdevLinux::UdevMonitorFilter> filters;
   filters.push_back(UdevLinux::UdevMonitorFilter(kInputSubsystem, NULL));
   udev_.reset(new UdevLinux(
@@ -86,12 +92,7 @@ GamepadPlatformDataFetcherLinux::GamepadPlatformDataFetcherLinux() {
   EnumerateDevices();
 }
 
-GamepadPlatformDataFetcherLinux::~GamepadPlatformDataFetcherLinux() {
-  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i)
-    CloseFileDescriptorIfValid(device_fd_[i]);
-}
-
-void GamepadPlatformDataFetcherLinux::GetGamepadData(WebGamepads* pads, bool) {
+void GamepadPlatformDataFetcherLinux::GetGamepadData(bool) {
   TRACE_EVENT0("GAMEPAD", "GetGamepadData");
 
   // Update our internal state.
@@ -100,11 +101,6 @@ void GamepadPlatformDataFetcherLinux::GetGamepadData(WebGamepads* pads, bool) {
       ReadDeviceData(i);
     }
   }
-
-  pads->length = WebGamepads::itemsLengthCap;
-  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
-    MapAndSanitizeGamepadData(&pad_state_[i], &pads->items[i]);
-  }
 }
 
 // Used during enumeration, and monitor notifications.
@@ -113,8 +109,6 @@ void GamepadPlatformDataFetcherLinux::RefreshDevice(udev_device* dev) {
   std::string node_path;
   if (IsGamepad(dev, &index, &node_path)) {
     int& device_fd = device_fd_[index];
-    WebGamepad& pad = pad_state_[index].data;
-    GamepadStandardMappingFunction& mapper = pad_state_[index].mapper;
 
     CloseFileDescriptorIfValid(device_fd);
 
@@ -127,17 +121,26 @@ void GamepadPlatformDataFetcherLinux::RefreshDevice(udev_device* dev) {
     if (!dev) {
       // Unable to get device information, don't use this device.
       device_fd = -1;
-      pad.connected = false;
       return;
     }
 
     device_fd = HANDLE_EINTR(open(node_path.c_str(), O_RDONLY | O_NONBLOCK));
     if (device_fd < 0) {
       // Unable to open device, don't use.
-      pad.connected = false;
       return;
     }
 
+    PadState* state = GetPadState(index);
+    if (!state) {
+      // No slot available for device, don't use.
+      CloseFileDescriptorIfValid(device_fd);
+      device_fd = -1;
+      return;
+    }
+
+    WebGamepad& pad = state->data;
+    GamepadStandardMappingFunction& mapper = state->mapper;
+
     const char* vendor_id = udev_device_get_sysattr_value(dev, "id/vendor");
     const char* product_id = udev_device_get_sysattr_value(dev, "id/product");
     mapper = GetGamepadStandardMappingFunction(vendor_id, product_id);
@@ -194,9 +197,6 @@ void GamepadPlatformDataFetcherLinux::RefreshDevice(udev_device* dev) {
       pad.mapping[0] = 0;
     }
 
-    pad_state_[index].axis_mask = 0;
-    pad_state_[index].button_mask = 0;
-
     pad.connected = true;
   }
 }
@@ -234,10 +234,15 @@ void GamepadPlatformDataFetcherLinux::ReadDeviceData(size_t index) {
     return;
   }
 
-  const int& fd = device_fd_[index];
-  WebGamepad& pad = pad_state_[index].data;
+  PadState* state = GetPadState(index);
+  if (!state)
+    return;
+
+  int fd = device_fd_[index];
   DCHECK_GE(fd, 0);
 
+  WebGamepad& pad = state->data;
+
   js_event event;
   while (HANDLE_EINTR(read(fd, &event, sizeof(struct js_event))) > 0) {
     size_t item = event.number;