Refactored gamepad polling to support dynamic sources

device/gamepad/gamepad_platform_data_fetcher_android.cc

Index: device/gamepad/gamepad_platform_data_fetcher_android.cc
diff --git a/device/gamepad/gamepad_platform_data_fetcher_android.cc b/device/gamepad/gamepad_platform_data_fetcher_android.cc
index 9a14515f608e5275e1574dbde315b25a8e1faa05..58e3fd94e01a33bec70f8cb7f504b26ad258d74e 100644
--- a/device/gamepad/gamepad_platform_data_fetcher_android.cc
+++ b/device/gamepad/gamepad_platform_data_fetcher_android.cc
@@ -34,25 +34,29 @@ bool GamepadPlatformDataFetcherAndroid::
 }
 
 GamepadPlatformDataFetcherAndroid::GamepadPlatformDataFetcherAndroid() {
-  PauseHint(false);
 }
 
 GamepadPlatformDataFetcherAndroid::~GamepadPlatformDataFetcherAndroid() {
   PauseHint(true);
 }
 
+GamepadSource GamepadPlatformDataFetcherAndroid::source() {
+  return Factory::static_source();
+}
+
+void GamepadPlatformDataFetcherAndroid::OnAddedToProvider() {
+  PauseHint(false);
+}
+
 void GamepadPlatformDataFetcherAndroid::GetGamepadData(
-    blink::WebGamepads* pads,
     bool devices_changed_hint) {
   TRACE_EVENT0("GAMEPAD", "GetGamepadData");
 
-  pads->length = 0;
-
   JNIEnv* env = AttachCurrentThread();
   if (!env)
     return;
 
-  Java_GamepadList_updateGamepadData(env, reinterpret_cast<intptr_t>(pads));
+  Java_GamepadList_updateGamepadData(env, reinterpret_cast<intptr_t>(this));
 }
 
 void GamepadPlatformDataFetcherAndroid::PauseHint(bool paused) {
@@ -65,7 +69,7 @@ void GamepadPlatformDataFetcherAndroid::PauseHint(bool paused) {
 
 static void SetGamepadData(JNIEnv* env,
                            const JavaParamRef<jobject>& obj,
-                           jlong gamepads,
+                           jlong data_fetcher,
                            jint index,
                            jboolean mapping,
                            jboolean connected,
@@ -73,45 +77,44 @@ static void SetGamepadData(JNIEnv* env,
                            jlong timestamp,
                            const JavaParamRef<jfloatArray>& jaxes,
                            const JavaParamRef<jfloatArray>& jbuttons) {
-  DCHECK(gamepads);
-  blink::WebGamepads* pads = reinterpret_cast<WebGamepads*>(gamepads);
-  DCHECK_EQ(pads->length, unsigned(index));
+  DCHECK(data_fetcher);
+  GamepadPlatformDataFetcherAndroid* fetcher =
+      reinterpret_cast<GamepadPlatformDataFetcherAndroid*>(data_fetcher);
   DCHECK_LT(index, static_cast<int>(blink::WebGamepads::itemsLengthCap));
 
-  ++pads->length;
-
-  blink::WebGamepad& pad = pads->items[index];
-
-  pad.connected = connected;
-
-  pad.timestamp = timestamp;
-
   // Do not set gamepad parameters for all the gamepad devices that are not
   // attached.
   if (!connected)
     return;
 
-  // Map the Gamepad DeviceName String to the WebGamepad Id. Ideally it should
-  // be mapped to vendor and product information but it is only available at
-  // kernel level and it can not be queried using class
-  // android.hardware.input.InputManager.
-  // TODO(SaurabhK): Store a cached WebGamePad object in
-  // GamepadPlatformDataFetcherAndroid and only update constant WebGamepad
-  // values when a device has changed.
-  base::string16 device_name;
-  base::android::ConvertJavaStringToUTF16(env, devicename, &device_name);
-  const size_t name_to_copy =
-      std::min(device_name.size(), WebGamepad::idLengthCap - 1);
-  memcpy(pad.id, device_name.data(),
-         name_to_copy * sizeof(base::string16::value_type));
-  pad.id[name_to_copy] = 0;
-
-  base::string16 mapping_name = base::UTF8ToUTF16(mapping ? "standard" : "");
-  const size_t mapping_to_copy =
-      std::min(mapping_name.size(), WebGamepad::mappingLengthCap - 1);
-  memcpy(pad.mapping, mapping_name.data(),
-         mapping_to_copy * sizeof(base::string16::value_type));
-  pad.mapping[mapping_to_copy] = 0;
+  PadState* state = fetcher->GetPadState(index);
+
+  if (!state)
+    return;
+
+  blink::WebGamepad& pad = state->data;
+
+  // Is this the first time we've seen this device?
+  if (state->active_state == GAMEPAD_NEWLY_ACTIVE) {
+    // Map the Gamepad DeviceName String to the WebGamepad Id. Ideally it should
+    // be mapped to vendor and product information but it is only available at
+    // kernel level and it can not be queried using class
+    // android.hardware.input.InputManager.
+    base::string16 device_name;
+    base::android::ConvertJavaStringToUTF16(env, devicename, &device_name);
+    const size_t name_to_copy =
+        std::min(device_name.size(), WebGamepad::idLengthCap - 1);
+    memcpy(pad.id, device_name.data(),
+           name_to_copy * sizeof(base::string16::value_type));
+    pad.id[name_to_copy] = 0;
+
+    base::string16 mapping_name = base::UTF8ToUTF16(mapping ? "standard" : "");
+    const size_t mapping_to_copy =
+        std::min(mapping_name.size(), WebGamepad::mappingLengthCap - 1);
+    memcpy(pad.mapping, mapping_name.data(),
+           mapping_to_copy * sizeof(base::string16::value_type));
+    pad.mapping[mapping_to_copy] = 0;
+  }
 
   pad.timestamp = timestamp;