Support setting mouse cursor icon in Android N.

chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java
index 168d3c4cc24bc64db8a153a908221680ec714e92..084f5c0c98c55e2da7601e25ecbe332755ca684c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabViewAndroidDelegate.java
@@ -4,6 +4,8 @@
 
 package org.chromium.chrome.browser.tab;
 
+import android.os.Build;
+import android.view.PointerIcon;
 import android.view.ViewGroup;
 
 import org.chromium.ui.base.ViewAndroidDelegate;
@@ -47,4 +49,11 @@ class TabViewAndroidDelegate extends ViewAndroidDelegate {
     public ViewGroup getContainerView() {
         return mContainerView;
     }
+
+    @Override
+    public void updatePointerIcon(PointerIcon icon) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            getContainerView().getRootView().setPointerIcon(icon);

[Ted C, 2017/06/07 19:27:18]

since this mutates the root view, what happens in cases where the tab crashes,
the tab is switched to another tab via a keyboard shortcut, the mouse is
disconnected, move focus outside of the view (i.e. it is full page textarea in
the web contents but you move to the omnibox, does it get reset)?

is this called often enough to reset to the initial value?  I just want to make
sure that we don't leave the cursor in a bad state ever.

[jaebaek, 2017/06/08 01:00:11]

It seems we cannot make the pointer icon visible by setting it in the container
view.
(as far as I tested, we must set it to parent of parent of container view)

When testing cases you mentioned:
tab crashes --> the pointer icon disappears.
(it becomes visible when I move it)
switch to another tab --> the same as tab crashes.
mouse disconnected --> the pointer icon remains around 10 seconds and
disappears.
move focus outside of the view --> it gets reset.

When observing its behavior:
move event --> it is updated quickly (almost realtime).
keyboard or touch event --> disappears after 1 second.
(during the short time until it disappears, it is updated if needed)
no event --> the pointer icon remains around 10 seconds and disappears.
(the same as mouse disconnected)

It looks fine, but I also dislike this hacky solution .. let me check why we
cannot change the pointer icon only by setting it to the container view.

+        }
+    }
 }