Switch tabs from VR shell.

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
index 0f77bac3a8720683f42e4b455d0f651048ec52d8..f869c721b3ef0eb628efba20c3d923504cdd398c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
@@ -35,6 +35,8 @@ import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.ChromeTabbedActivity;
 import org.chromium.chrome.browser.multiwindow.MultiWindowUtils;
 import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tabmodel.TabModel;
+import org.chromium.chrome.browser.tabmodel.TabModelUtils;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -627,6 +629,19 @@ public class VrShellDelegate {
         return mNativeVrShellDelegate;
     }
 
+    @CalledByNative
+    private void showTab(int id) {
+        Tab tab = mActivity.getTabModelSelector().getTabById(id);
+        if (tab != null) {

[cjgrant, 2017/02/10 16:02:15]

Should this be an early return instead?

[tiborg, 2017/02/10 16:34:17]

You mean instead of the nested if statements?

[cjgrant, 2017/02/10 18:14:29]

Yes.  That's the preference, to avoid excessive indentation, and make sure that
the typical execution path is clear.

[tiborg, 2017/02/13 17:35:37]

Done.

+            int index = mActivity.getTabModelSelector().getModel(tab.isIncognito()).indexOf(tab);

[tiborg, 2017/02/09 21:22:00]

I don't know why this line and the one below are so long. It's the result of
'git cl format'.

[mthiesse, 2017/02/09 21:37:56]

java lines are 100 characters long.

+
+            if (index != TabModel.INVALID_TAB_INDEX) {
+                TabModelUtils.setIndex(
+                        mActivity.getTabModelSelector().getModel(tab.isIncognito()), index);
+            }
+        }
+    }

[tiborg, 2017/02/09 21:22:00]

What would be the best way to deal with an unknown tab ID? Just ignore (like it
is right now), exception, or something else?

[mthiesse, 2017/02/09 21:37:56]

Yeah, ignoring it is probably best. 

+
     private native long nativeInit();
     private native void nativeSetPresentResult(long nativeVrShellDelegate, boolean result);
     private native void nativeDisplayActivate(long nativeVrShellDelegate);