Add support for touch events on Android

Currently on Android we treat all touch events as scroll events. Servo
is already capable of distinguishing between scroll-touches and regular
touch events (see `on_touch_move` in `components/compositor/touch.rs`),
so we should just be passing touch events through.

Servo however does not natively support fling gestures, so we continue
to use `GestureDetector` for that.

ports/libsimpleservo/src/api.rs

@@ -9,7 +9,7 @@ use servo::embedder_traits::resources::{self, Resource};
 use servo::embedder_traits::EmbedderMsg;
 use servo::euclid::{TypedPoint2D, TypedScale, TypedSize2D, TypedVector2D};
 use servo::msg::constellation_msg::TraversalDirection;
-use servo::script_traits::{MouseButton, TouchEventType};
+use servo::script_traits::{MouseButton, TouchEventType, TouchId};
 use servo::servo_config::opts;
 use servo::servo_config::prefs::{PrefValue, PREFS};
 use servo::servo_url::ServoUrl;
@@ -312,6 +312,46 @@ impl ServoGlue {
         self.process_event(event)
     }
 
+    /// Touch event: press down
+    pub fn touch_down(&mut self, x: f32, y: f32, pointer_id: i32) -> Result<(), &'static str> {
+        let event = WindowEvent::Touch(
+            TouchEventType::Down,
+            TouchId(pointer_id),
+            TypedPoint2D::new(x as f32, y as f32),
+        );
+        self.process_event(event)
+    }
+
+    /// Touch event: move touching finger
+    pub fn touch_move(&mut self, x: f32, y: f32, pointer_id: i32) -> Result<(), &'static str> {
+        let event = WindowEvent::Touch(
+            TouchEventType::Move,
+            TouchId(pointer_id),
+            TypedPoint2D::new(x as f32, y as f32),
+        );
+        self.process_event(event)
+    }
+
+    /// Touch event: Lift touching finger
+    pub fn touch_up(&mut self, x: f32, y: f32, pointer_id: i32) -> Result<(), &'static str> {
+        let event = WindowEvent::Touch(
+            TouchEventType::Up,
+            TouchId(pointer_id),
+            TypedPoint2D::new(x as f32, y as f32),
+        );
+        self.process_event(event)
+    }
+
+    /// Cancel touch event
+    pub fn touch_cancel(&mut self, x: f32, y: f32, pointer_id: i32) -> Result<(), &'static str> {
+        let event = WindowEvent::Touch(
+            TouchEventType::Cancel,
+            TouchId(pointer_id),
+            TypedPoint2D::new(x as f32, y as f32),
+        );
+        self.process_event(event)
+    }
+
     /// Start pinchzoom.
     /// x/y are pinch origin coordinates.
     pub fn pinchzoom_start(&mut self, factor: f32, _x: u32, _y: u32) -> Result<(), &'static str> {

ports/libsimpleservo/src/capi.rs

@@ -205,6 +205,30 @@ pub extern "C" fn scroll(dx: i32, dy: i32, x: i32, y: i32) {
     call(|s| s.scroll(dx as i32, dy as i32, x as u32, y as u32));
 }
 
+#[no_mangle]
+pub extern "C" fn touch_down(x: f32, y: f32, pointer_id: i32) {
+    debug!("touch down");
+    call(|s| s.touch_down(x, y, pointer_id));
+}
+
+#[no_mangle]
+pub extern "C" fn touch_up(x: f32, y: f32, pointer_id: i32) {
+    debug!("touch up");
+    call(|s| s.touch_up(x, y, pointer_id));
+}
+
+#[no_mangle]
+pub extern "C" fn touch_move(x: f32, y: f32, pointer_id: i32) {
+    debug!("touch move");
+    call(|s| s.touch_move(x, y, pointer_id));
+}
+
+#[no_mangle]
+pub extern "C" fn touch_cancel(x: f32, y: f32, pointer_id: i32) {
+    debug!("touch cancel");
+    call(|s| s.touch_cancel(x, y, pointer_id));
+}
+
 #[no_mangle]
 pub extern "C" fn pinchzoom_start(factor: f32, x: i32, y: i32) {
     debug!("pinchzoom_start");

ports/libsimpleservo/src/jniapi.rs

@@ -230,6 +230,54 @@ pub fn Java_org_mozilla_servoview_JNIServo_scroll(
     call(&env, |s| s.scroll(dx as i32, dy as i32, x as u32, y as u32));
 }
 
+#[no_mangle]
+pub fn Java_org_mozilla_servoview_JNIServo_touchDown(
+    env: JNIEnv,
+    _: JClass,
+    x: jfloat,
+    y: jfloat,
+    pointer_id: jint,
+) {
+    debug!("touchDown");
+    call(&env, |s| s.touch_down(x, y, pointer_id as i32));
+}
+
+#[no_mangle]
+pub fn Java_org_mozilla_servoview_JNIServo_touchUp(
+    env: JNIEnv,
+    _: JClass,
+    x: jfloat,
+    y: jfloat,
+    pointer_id: jint,
+) {
+    debug!("touchUp");
+    call(&env, |s| s.touch_up(x, y, pointer_id as i32));
+}
+
+#[no_mangle]
+pub fn Java_org_mozilla_servoview_JNIServo_touchMove(
+    env: JNIEnv,
+    _: JClass,
+    x: jfloat,
+    y: jfloat,
+    pointer_id: jint,
+) {
+    debug!("touchMove");
+    call(&env, |s| s.touch_move(x, y, pointer_id as i32));
+}
+
+#[no_mangle]
+pub fn Java_org_mozilla_servoview_JNIServo_touchCancel(
+    env: JNIEnv,
+    _: JClass,
+    x: jfloat,
+    y: jfloat,
+    pointer_id: jint,
+) {
+    debug!("touchCancel");
+    call(&env, |s| s.touch_cancel(x, y, pointer_id as i32));
+}
+
 #[no_mangle]
 pub fn Java_org_mozilla_servoview_JNIServo_pinchZoomStart(
     env: JNIEnv,