Add EventForwarder for routing touch events

ui/android/java/src/org/chromium/ui/base/SPenSupport.java

Index: ui/android/java/src/org/chromium/ui/base/SPenSupport.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/SPenSupport.java b/ui/android/java/src/org/chromium/ui/base/SPenSupport.java
similarity index 77%
rename from content/public/android/java/src/org/chromium/content/browser/SPenSupport.java
rename to ui/android/java/src/org/chromium/ui/base/SPenSupport.java
index 62fb90c6fcea95734d7bdffe3878bb98eb98b21f..9aae52aa7fc58527a5e11663e402e8dae87be32f 100644
--- a/content/public/android/java/src/org/chromium/content/browser/SPenSupport.java
+++ b/ui/android/java/src/org/chromium/ui/base/SPenSupport.java
@@ -1,8 +1,8 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-package org.chromium.content.browser;
+package org.chromium.ui.base;
 
 import android.content.Context;
 import android.content.pm.FeatureInfo;
@@ -13,7 +13,6 @@ import android.view.MotionEvent;
  * Support S-Pen event detection and conversion.
  */
 public final class SPenSupport {

[boliu, 2017/02/27 19:21:57]

I think we don't need to expose this at all, just detect lazily?

[Jinsuk Kim, 2017/02/28 06:56:04]

This is used by Chrome too. See CompositorViewHolder. The reason I split detect
/ convert is for the callsites of convert not to have to pass |context| which is
used only for detection.

[boliu, 2017/02/28 22:44:54]

ok, I guess hiding this needs to come after chrome refactoring is done

but I think lazy detect is still a good idea

[Jinsuk Kim, 2017/03/02 04:08:34]

I agree. Left a TODO for that. I think it gets easier to do that once
EventHandler (or ViewRoot) later has an access to WindowAndroid which can
provide |Context|.

-
     // These values are obtained from Samsung.
     private static final int SPEN_ACTION_DOWN = 211;
     private static final int SPEN_ACTION_UP = 212;
@@ -21,28 +20,22 @@ public final class SPenSupport {
     private static final int SPEN_ACTION_CANCEL = 214;
     private static Boolean sIsSPenSupported;
 
-    /**
-     * @return Whether SPen is supported on the device.
-     */
-    public static boolean isSPenSupported(Context context) {
-        if (sIsSPenSupported == null) {
-            sIsSPenSupported = detectSPenSupport(context);
-        }
-        return sIsSPenSupported.booleanValue();
-    }
+    public static void detect(Context context) {
+        if (sIsSPenSupported != null) return;
 
-    private static boolean detectSPenSupport(Context context) {
         if (!"SAMSUNG".equalsIgnoreCase(Build.MANUFACTURER)) {
-            return false;
+            sIsSPenSupported = false;
+            return;
         }
 
         final FeatureInfo[] infos = context.getPackageManager().getSystemAvailableFeatures();
         for (FeatureInfo info : infos) {
             if ("com.sec.feature.spen_usp".equalsIgnoreCase(info.name)) {
-                return true;
+                sIsSPenSupported = true;
+                return;
             }
         }
-        return false;
+        sIsSPenSupported = false;
     }
 
     /**
@@ -53,6 +46,9 @@ public final class SPenSupport {
      * @return Event action after the conversion.
      */
     public static int convertSPenEventAction(int eventActionMasked) {
+        assert sIsSPenSupported != null;

[boliu, 2017/02/27 19:21:57]

how is client supposed to know if detect succeeded or failed?

[Jinsuk Kim, 2017/02/28 06:56:04]

? |sIsSPenSupported| will either be true or false.

FYI SPenSupport.detect() needs to be invoked in advance. That's where
sIsPenSupported is initialized. assert is here to guard against use without
init. Added a comment to clarify it. 

[boliu, 2017/02/28 22:44:54]

oh oops, misread, I thought it's "assert sIsSPenSupported" check..

[Jinsuk Kim, 2017/03/02 04:08:34]

Acknowledged.

+        if (!sIsSPenSupported.booleanValue()) return eventActionMasked;
+
         // S-Pen support: convert to normal stylus event handling
         switch (eventActionMasked) {
             case SPEN_ACTION_DOWN: