VR: Update back button state in more places.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
index 8824e21e99662bfb98d43c4f217c879dacb1eb55..2181b4a2607ffe8ddfa6b0643d13b44e6dcd507d 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
@@ -97,6 +97,8 @@ public class VrShellImpl
     private Tab mTab;
     private ContentViewCore mContentViewCore;
     private NativePage mNativePage;
+    private Boolean mCanGoBack;
+    private Boolean mCanGoForward;
 
     private WindowAndroid mOriginalWindowAndroid;
     private VrWindowAndroid mContentVrWindowAndroid;
@@ -215,6 +217,28 @@ public class VrShellImpl
                 if (mNativeVrShell == 0) return;
                 nativeOnLoadProgressChanged(mNativeVrShell, progress / 100.0);
             }
+
+            @Override
+            public void onCrash(Tab tab, boolean sadTabShown) {
+                updateHistoryButtonsVisibility();
+            }
+
+            @Override
+            public void onLoadStarted(Tab tab, boolean toDifferentDocument) {
+                if (!toDifferentDocument) return;
+                updateHistoryButtonsVisibility();
+            }
+
+            @Override
+            public void onLoadStopped(Tab tab, boolean toDifferentDocument) {
+                if (!toDifferentDocument) return;
+                updateHistoryButtonsVisibility();

[bshe, 2017/06/08 15:04:19]

Is this needed? In ToolbarManager.java, it doesnt seem to update navigation
button visibility when load stopped.

[mthiesse, 2017/06/08 15:07:44]

In ToolbarManager.java it calls updateTabLoadingState(true), which calls
updateButtonStatus(), so it does update button visibility.

+            }
+
+            @Override
+            public void onUrlUpdated(Tab tab) {
+                updateHistoryButtonsVisibility();
+            }
         };
 
         mTabModelSelectorObserver = new EmptyTabModelSelectorObserver() {
@@ -297,6 +321,7 @@ public class VrShellImpl
         createTabList();
         mActivity.getTabModelSelector().addObserver(mTabModelSelectorObserver);
         createTabModelSelectorTabObserver();
+        updateHistoryButtonsVisibility();
 
         mPresentationView.setOnTouchListener(mTouchListener);
     }
@@ -614,7 +639,14 @@ public class VrShellImpl
         boolean shouldAlwaysGoBack = mActivity instanceof ChromeTabbedActivity
                 && (mNativePage == null || !(mNativePage instanceof NewTabPage));
         boolean canGoBack = mTab.canGoBack() || shouldAlwaysGoBack;
-        nativeSetHistoryButtonsEnabled(mNativeVrShell, canGoBack, mTab.canGoForward());
+        boolean canGoForward = mTab.canGoForward();
+        if ((mCanGoBack != null && canGoBack == mCanGoBack)
+                && (mCanGoForward != null && canGoForward == mCanGoForward)) {
+            return;
+        }
+        mCanGoBack = canGoBack;
+        mCanGoForward = canGoForward;
+        nativeSetHistoryButtonsEnabled(mNativeVrShell, mCanGoBack, mCanGoForward);
     }
 
     @CalledByNative