Introduce ViewRoot to forward input/view events to native

ui/android/BUILD.gn

Index: ui/android/BUILD.gn
diff --git a/ui/android/BUILD.gn b/ui/android/BUILD.gn
index d75680cd2feba64655832a81f4cccd15c8380550..cda3ddb0c2af6a78d14430534bd5c35f750c1787 100644
--- a/ui/android/BUILD.gn
+++ b/ui/android/BUILD.gn
@@ -23,6 +23,8 @@ component("android") {
     "edge_effect_base.h",
     "edge_effect_l.cc",
     "edge_effect_l.h",
+    "event_handler.cc",
+    "event_handler.h",
     "overscroll_glow.cc",
     "overscroll_glow.h",
     "overscroll_refresh.cc",
@@ -40,6 +42,8 @@ component("android") {
     "ui_android_jni_registrar.h",
     "view_android.cc",
     "view_android.h",
+    "view_client.cc",
+    "view_client.h",
     "window_android.cc",
     "window_android.h",
     "window_android_compositor.h",
@@ -76,6 +80,7 @@ static_library("test_support") {
 
 generate_jni("ui_android_jni_headers") {
   sources = [
+    "java/src/org/chromium/ui/base/EventHandler.java",
     "java/src/org/chromium/ui/base/ViewAndroidDelegate.java",
     "java/src/org/chromium/ui/base/WindowAndroid.java",
     "java/src/org/chromium/ui/display/DisplayAndroidManager.java",
@@ -166,6 +171,7 @@ android_library("ui_java") {
     "java/src/org/chromium/ui/base/AndroidPermissionDelegate.java",
     "java/src/org/chromium/ui/base/Clipboard.java",
     "java/src/org/chromium/ui/base/DeviceFormFactor.java",
+    "java/src/org/chromium/ui/base/EventHandler.java",
     "java/src/org/chromium/ui/base/LocalizationUtils.java",
     "java/src/org/chromium/ui/base/ResourceBundle.java",
     "java/src/org/chromium/ui/base/SelectFileDialog.java",