Introduce ViewRoot forwarding input/view events to native

content/shell/android/java/src/org/chromium/content_shell/Shell.java

Index: content/shell/android/java/src/org/chromium/content_shell/Shell.java
diff --git a/content/shell/android/java/src/org/chromium/content_shell/Shell.java b/content/shell/android/java/src/org/chromium/content_shell/Shell.java
index e2f82e34584bb68430d33a6a1396760ae116293b..47e8da6a42962c8a3eef3eec75a690405fc971b2 100644
--- a/content/shell/android/java/src/org/chromium/content_shell/Shell.java
+++ b/content/shell/android/java/src/org/chromium/content_shell/Shell.java
@@ -37,6 +37,7 @@ import org.chromium.content_public.browser.LoadUrlParams;
 import org.chromium.content_public.browser.NavigationController;
 import org.chromium.content_public.browser.WebContents;
 import org.chromium.ui.base.ViewAndroidDelegate;
+import org.chromium.ui.base.ViewRoot;
 import org.chromium.ui.base.WindowAndroid;
 
 /**
@@ -297,7 +298,7 @@ public class Shell extends LinearLayout {
         mContentViewCore = new ContentViewCore(context, "");
         ContentView cv = ContentView.createContentView(context, mContentViewCore);
         mContentViewCore.initialize(ViewAndroidDelegate.createBasicDelegate(cv), cv,
-                webContents, mWindow);
+                webContents, ViewRoot.create(mWindow));

[boliu, 2017/01/05 19:09:28]

first question is what calls destroy?

Then after digging, the right thing here again is that ViewRoot should be
created *next* to where WindowAndroid is created, so in this case, in
ContentShellActivity. However, then also realized that WindowAndroid isn't
destroyed either, which is an existing bug.

I still haven't read other embedders (other than webview) yet, but make sure
destroy is called in all the places

[Jinsuk Kim, 2017/01/05 22:30:15]

Shouldn't it be created where 'content' is created? Though in this embedder WA :
VR is 1-1 there relationship is 1-multiple in general, and view root is created
per content.

But then in the latest comments I can see that the discussion you guys had kind
of concluded it is rather per-tab (or CompositorView) where there can be
multiple contents (overlay panel for contextual search, mobile view, etc) -
specifically for Chrome. 

I still can't get my head around how a single ViewRoot can deal with multiple
web contents. I'll come up with either a new patch or a new question soon.
Done. destroyed when Shell (and its CVC) is destroyed for now.

[boliu, 2017/01/05 22:39:38]

No, except webview. If it weren't for webview, ViewRoot and WindowAndroid would
be the same class. Which means other than webview, ViewRoot and WindowAndroid
should have the exact same life time.

         mContentViewCore.setActionModeCallback(defaultActionCallback());
         mContentViewCore.setContentViewClient(mContentViewClient);
         mWebContents = mContentViewCore.getWebContents();