Add EventForwarder for routing touch events

content/browser/web_contents/web_contents_view_android.cc

Index: content/browser/web_contents/web_contents_view_android.cc
diff --git a/content/browser/web_contents/web_contents_view_android.cc b/content/browser/web_contents/web_contents_view_android.cc
index eed15aa9d3d3221af5a8ee13ab78e681e0e9bdf6..7129cc9e4eafa201090293faec300dbb1039da29 100644
--- a/content/browser/web_contents/web_contents_view_android.cc
+++ b/content/browser/web_contents/web_contents_view_android.cc
@@ -10,15 +10,16 @@
 #include "cc/layers/layer.h"
 #include "content/browser/android/content_view_core_impl.h"
 #include "content/browser/frame_host/interstitial_page_impl.h"
-#include "content/browser/renderer_host/render_widget_host_view_android.h"
 #include "content/browser/renderer_host/render_view_host_factory.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
+#include "content/browser/renderer_host/render_widget_host_view_android.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/common/drop_data.h"
 #include "ui/android/overscroll_refresh_handler.h"
 #include "ui/display/screen.h"
+#include "ui/events/android/motion_event_android.h"
 #include "ui/gfx/android/java_bitmap.h"
 #include "ui/gfx/image/image_skia.h"
 
@@ -82,8 +83,8 @@ WebContentsViewAndroid::WebContentsViewAndroid(
     : web_contents_(web_contents),
       content_view_core_(NULL),
       delegate_(delegate),
-      synchronous_compositor_client_(nullptr) {
-}
+      view_(this),
+      synchronous_compositor_client_(nullptr) {}
 
 WebContentsViewAndroid::~WebContentsViewAndroid() {
   if (view_.GetLayer())
@@ -395,4 +396,11 @@ void WebContentsViewAndroid::TakeFocus(bool reverse) {
   web_contents_->GetRenderWidgetHostView()->Focus();
 }
 
+bool WebContentsViewAndroid::OnTouchEvent(const ui::MotionEventAndroid& event,
+                                          bool for_touch_handle) {
+  if (event.GetAction() == ui::MotionEventAndroid::ACTION_DOWN)
+    content_view_core_->OnTouchDown(event.GetJavaObject());
+  return false;  // let the children handle the actual event.

[Khushal, 2017/03/03 23:36:07]

Don't you always go to the child first, before giving the ancestor a chance to
handle the event?

[Jinsuk Kim, 2017/03/06 04:07:33]

Good catch. After some thought, I changed the checking order from parent to
child. ViewAndroid tree hierarchy (WCVA -> RWHVA) does not (or has to) follow
the Android UI view hierarchy -  they always are of the same layout, and the
order in which an event is handled can be independent of Java layer. Android
view order is reflected in the order of sibling VA's of WCVA, which determines
which content is at the front and should receive an event first.

[Khushal, 2017/03/07 04:17:07]

I think android just uses a different callback for giving the event to the
parent first (onInterceptTouchEvent). But this works well too. :)

+}
+
 } // namespace content